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 $116.84   8.441%   $126.7025   $126.70   $126.70   $126.70  
  Purchase #2 $202.54   3.114%   $208.8471   $208.85   $208.85   $208.80  
  Purchase #3 $51.45   13.104%   $58.192   $58.19   $58.20   $58.20  
  Purchase #4 $163.53   3.419%   $169.1211   $169.12   $169.10   $169.10  
  Purchase #5 $121.41   9.342%   $132.7521   $132.75   $132.75   $132.80  
  Purchase #6 $149.70   5.221%   $157.5158   $157.52   $157.50   $157.50  
  Purchase #7 $153.34   3.183%   $158.2208   $158.22   $158.20   $158.20  
  7 purchase totals = $958.81       $1,011.3514   $1,011.35   $1,011.30   $1,011.30