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 $148.88   12.187%   $167.024   $167.02   $167.00   $167.00  
  Purchase #2 $59.63   13.871%   $67.9013   $67.90   $67.90   $67.90  
  Purchase #3 $50.71   10.132%   $55.8479   $55.85   $55.85   $55.80  
  Purchase #4 $119.82   4.536%   $125.255   $125.26   $125.25   $125.30  
  Purchase #5 $33.39   11.350%   $37.1798   $37.18   $37.20   $37.20  
  Purchase #6 $82.68   4.171%   $86.1286   $86.13   $86.15   $86.10  
  Purchase #7 $222.42   11.385%   $247.7425   $247.74   $247.75   $247.70  
  7 purchase totals = $717.53       $787.0791   $787.08   $787.10   $787.00