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 $59.60   5.330%   $62.7767   $62.78   $62.80   $62.80  
  Purchase #2 $100.86   12.160%   $113.1246   $113.12   $113.10   $113.10  
  Purchase #3 $222.99   10.418%   $246.2211   $246.22   $246.20   $246.20  
  Purchase #4 $161.73   10.265%   $178.3316   $178.33   $178.35   $178.30  
  Purchase #5 $8.87   12.271%   $9.9584   $9.96   $9.95   $10.00  
  Purchase #6 $160.97   4.588%   $168.3553   $168.36   $168.35   $168.40  
  Purchase #7 $45.94   3.623%   $47.6044   $47.60   $47.60   $47.60  
  7 purchase totals = $760.96       $826.3721   $826.37   $826.35   $826.40