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 $87.53   8.295%   $94.7906   $94.79   $94.80   $94.80  
  Purchase #2 $111.96   3.610%   $116.0018   $116.00   $116.00   $116.00  
  Purchase #3 $53.81   10.381%   $59.396   $59.40   $59.40   $59.40  
  Purchase #4 $19.85   11.323%   $22.0976   $22.10   $22.10   $22.10  
  Purchase #5 $53.28   8.643%   $57.885   $57.89   $57.90   $57.90  
  Purchase #6 $64.37   7.228%   $69.0227   $69.02   $69.00   $69.00  
  Purchase #7 $211.36   11.543%   $235.7573   $235.76   $235.75   $235.80  
  7 purchase totals = $602.16       $654.9510   $654.96   $654.95   $655.00