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 $207.65   4.653%   $217.312   $217.31   $217.30   $217.30  
  Purchase #2 $181.90   7.715%   $195.9336   $195.93   $195.95   $195.90  
  Purchase #3 $60.25   8.667%   $65.4719   $65.47   $65.45   $65.50  
  Purchase #4 $151.97   12.324%   $170.6988   $170.70   $170.70   $170.70  
  Purchase #5 $101.50   10.718%   $112.3788   $112.38   $112.40   $112.40  
  Purchase #6 $147.45   11.724%   $164.737   $164.74   $164.75   $164.70  
  Purchase #7 $200.55   12.685%   $225.9898   $225.99   $226.00   $226.00  
  7 purchase totals = $1,051.27       $1,152.5219   $1,152.52   $1,152.55   $1,152.50