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 $207.48   11.123%   $230.558   $230.56   $230.55   $230.60  
  Purchase #2 $226.63   7.270%   $243.106   $243.11   $243.10   $243.10  
  Purchase #3 $125.36   4.817%   $131.3986   $131.40   $131.40   $131.40  
  Purchase #4 $226.66   8.866%   $246.7557   $246.76   $246.75   $246.80  
  Purchase #5 $65.31   12.288%   $73.3353   $73.34   $73.35   $73.30  
  Purchase #6 $224.52   12.236%   $251.9923   $251.99   $252.00   $252.00  
  Purchase #7 $229.26   3.283%   $236.7866   $236.79   $236.80   $236.80  
  7 purchase totals = $1,305.22       $1,413.9325   $1,413.95   $1,413.95   $1,414.00