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 $43.32   8.351%   $46.9377   $46.94   $46.95   $46.90  
  Purchase #2 $206.98   13.122%   $234.1399   $234.14   $234.15   $234.10  
  Purchase #3 $80.71   5.738%   $85.3411   $85.34   $85.35   $85.30  
  Purchase #4 $87.90   3.805%   $91.2446   $91.24   $91.25   $91.20  
  Purchase #5 $47.30   6.318%   $50.2884   $50.29   $50.30   $50.30  
  Purchase #6 $53.33   12.867%   $60.192   $60.19   $60.20   $60.20  
  Purchase #7 $179.55   12.375%   $201.7693   $201.77   $201.75   $201.80  
  7 purchase totals = $699.09       $769.9130   $769.91   $769.95   $769.80