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 $116.35   7.411%   $124.9727   $124.97   $124.95   $125.00  
  Purchase #2 $137.36   10.675%   $152.0232   $152.02   $152.00   $152.00  
  Purchase #3 $177.54   6.341%   $188.7978   $188.80   $188.80   $188.80  
  Purchase #4 $171.31   13.472%   $194.3889   $194.39   $194.40   $194.40  
  Purchase #5 $195.74   6.760%   $208.972   $208.97   $208.95   $209.00  
  Purchase #6 $71.65   9.349%   $78.3486   $78.35   $78.35   $78.30  
  Purchase #7 $33.66   6.174%   $35.7382   $35.74   $35.75   $35.70  
  7 purchase totals = $903.61       $983.2414   $983.24   $983.20   $983.20