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 $197.41   8.428%   $214.0477   $214.05   $214.05   $214.00  
  Purchase #2 $35.32   5.400%   $37.2273   $37.23   $37.25   $37.20  
  Purchase #3 $154.88   8.442%   $167.955   $167.96   $167.95   $168.00  
  Purchase #4 $134.48   4.836%   $140.9835   $140.98   $141.00   $141.00  
  Purchase #5 $76.51   5.408%   $80.6477   $80.65   $80.65   $80.60  
  Purchase #6 $62.34   11.499%   $69.5085   $69.51   $69.50   $69.50  
  Purchase #7 $119.48   5.119%   $125.5962   $125.60   $125.60   $125.60  
  7 purchase totals = $780.42       $835.9659   $835.98   $836.00   $835.90