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 $64.57   5.606%   $68.1898   $68.19   $68.20   $68.20  
  Purchase #2 $231.84   11.269%   $257.966   $257.97   $257.95   $258.00  
  Purchase #3 $40.77   10.139%   $44.9037   $44.90   $44.90   $44.90  
  Purchase #4 $95.77   3.494%   $99.1162   $99.12   $99.10   $99.10  
  Purchase #5 $216.47   7.869%   $233.504   $233.50   $233.50   $233.50  
  Purchase #6 $120.42   9.132%   $131.4168   $131.42   $131.40   $131.40  
  Purchase #7 $97.90   11.147%   $108.8129   $108.81   $108.80   $108.80  
  7 purchase totals = $867.74       $943.9094   $943.91   $943.85   $943.90