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 $54.46   6.435%   $57.9645   $57.96   $57.95   $58.00  
  Purchase #2 $234.57   11.195%   $260.8301   $260.83   $260.85   $260.80  
  Purchase #3 $94.81   3.224%   $97.8667   $97.87   $97.85   $97.90  
  Purchase #4 $189.94   3.868%   $197.2869   $197.29   $197.30   $197.30  
  Purchase #5 $49.96   3.864%   $51.8905   $51.89   $51.90   $51.90  
  Purchase #6 $183.67   8.532%   $199.3407   $199.34   $199.35   $199.30  
  Purchase #7 $133.44   11.644%   $148.9778   $148.98   $149.00   $149.00  
  7 purchase totals = $940.85       $1,014.1572   $1,014.16   $1,014.20   $1,014.20