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 $67.52   4.751%   $70.7279   $70.73   $70.75   $70.70  
  Purchase #2 $191.53   11.605%   $213.7571   $213.76   $213.75   $213.80  
  Purchase #3 $81.51   6.155%   $86.5269   $86.53   $86.55   $86.50  
  Purchase #4 $85.44   7.792%   $92.0975   $92.10   $92.10   $92.10  
  Purchase #5 $191.88   6.336%   $204.0375   $204.04   $204.05   $204.00  
  Purchase #6 $18.34   4.849%   $19.2293   $19.23   $19.25   $19.20  
  Purchase #7 $67.41   11.732%   $75.3185   $75.32   $75.30   $75.30  
  7 purchase totals = $703.63       $761.6947   $761.71   $761.75   $761.60