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 $70.52   8.562%   $76.5579   $76.56   $76.55   $76.60  
  Purchase #2 $85.77   9.169%   $93.6343   $93.63   $93.65   $93.60  
  Purchase #3 $141.99   6.421%   $151.1072   $151.11   $151.10   $151.10  
  Purchase #4 $122.45   13.189%   $138.5999   $138.60   $138.60   $138.60  
  Purchase #5 $195.42   5.241%   $205.662   $205.66   $205.65   $205.70  
  Purchase #6 $171.95   10.306%   $189.6712   $189.67   $189.65   $189.70  
  Purchase #7 $86.96   11.643%   $97.0848   $97.08   $97.10   $97.10  
  7 purchase totals = $875.06       $952.3173   $952.31   $952.30   $952.40