Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $193.25   6.231%   $205.2914   $205.29   $205.30   $205.30  
  Purchase #2 $207.35   10.467%   $229.0533   $229.05   $229.05   $229.10  
  Purchase #3 $152.52   10.602%   $168.6902   $168.69   $168.70   $168.70  
  Purchase #4 $161.75   11.718%   $180.7039   $180.70   $180.70   $180.70  
  Purchase #5 $236.61   4.371%   $246.9522   $246.95   $246.95   $247.00  
  Purchase #6 $191.49   4.608%   $200.3139   $200.31   $200.30   $200.30  
  Purchase #7 $171.46   6.424%   $182.4746   $182.47   $182.45   $182.50  
  7 purchase totals = $1,314.43       $1,413.4795   $1,413.46   $1,413.45   $1,413.60