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 $45.84   6.562%   $48.848   $48.85   $48.85   $48.80  
  Purchase #2 $106.94   6.517%   $113.9093   $113.91   $113.90   $113.90  
  Purchase #3 $155.49   11.832%   $173.8876   $173.89   $173.90   $173.90  
  Purchase #4 $63.75   13.251%   $72.1975   $72.20   $72.20   $72.20  
  Purchase #5 $232.35   5.767%   $245.7496   $245.75   $245.75   $245.70  
  Purchase #6 $190.73   13.222%   $215.9483   $215.95   $215.95   $215.90  
  Purchase #7 $62.28   12.467%   $70.0444   $70.04   $70.05   $70.00  
  7 purchase totals = $857.38       $940.5847   $940.59   $940.60   $940.40