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 $87.41   10.432%   $96.5286   $96.53   $96.55   $96.50  
  Purchase #2 $202.85   6.461%   $215.9561   $215.96   $215.95   $216.00  
  Purchase #3 $126.35   10.560%   $139.6926   $139.69   $139.70   $139.70  
  Purchase #4 $210.57   3.292%   $217.502   $217.50   $217.50   $217.50  
  Purchase #5 $116.49   4.457%   $121.682   $121.68   $121.70   $121.70  
  Purchase #6 $92.54   7.212%   $99.214   $99.21   $99.20   $99.20  
  Purchase #7 $247.40   9.171%   $270.0891   $270.09   $270.10   $270.10  
  7 purchase totals = $1,083.61       $1,160.6644   $1,160.66   $1,160.70   $1,160.70