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 $95.86   9.152%   $104.6331   $104.63   $104.65   $104.60  
  Purchase #2 $216.80   7.115%   $232.2253   $232.23   $232.25   $232.20  
  Purchase #3 $29.55   10.760%   $32.7296   $32.73   $32.75   $32.70  
  Purchase #4 $35.42   4.380%   $36.9714   $36.97   $36.95   $37.00  
  Purchase #5 $227.96   11.421%   $253.9953   $254.00   $254.00   $254.00  
  Purchase #6 $24.44   7.210%   $26.2021   $26.20   $26.20   $26.20  
  Purchase #7 $243.37   7.181%   $260.8464   $260.85   $260.85   $260.80  
  7 purchase totals = $873.40       $947.6032   $947.61   $947.65   $947.50