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 $126.32   4.630%   $132.1686   $132.17   $132.15   $132.20  
  Purchase #2 $158.66   6.539%   $169.0348   $169.03   $169.05   $169.00  
  Purchase #3 $115.85   5.556%   $122.2866   $122.29   $122.30   $122.30  
  Purchase #4 $164.81   5.230%   $173.4296   $173.43   $173.45   $173.40  
  Purchase #5 $68.86   7.568%   $74.0713   $74.07   $74.05   $74.10  
  Purchase #6 $147.63   3.668%   $153.0451   $153.05   $153.05   $153.00  
  Purchase #7 $96.74   5.425%   $101.9881   $101.99   $102.00   $102.00  
  7 purchase totals = $878.87       $926.0241   $926.03   $926.05   $926.00