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 $195.91   13.719%   $222.7869   $222.79   $222.80   $222.80  
  Purchase #2 $175.93   10.500%   $194.4027   $194.40   $194.40   $194.40  
  Purchase #3 $244.56   3.114%   $252.1756   $252.18   $252.20   $252.20  
  Purchase #4 $68.69   3.637%   $71.1883   $71.19   $71.20   $71.20  
  Purchase #5 $110.83   6.645%   $118.1947   $118.19   $118.20   $118.20  
  Purchase #6 $87.79   5.318%   $92.4587   $92.46   $92.45   $92.50  
  Purchase #7 $63.35   7.692%   $68.2229   $68.22   $68.20   $68.20  
  7 purchase totals = $947.06       $1,019.4298   $1,019.43   $1,019.45   $1,019.50