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 $33.67   11.732%   $37.6202   $37.62   $37.60   $37.60  
  Purchase #2 $117.78   12.608%   $132.6297   $132.63   $132.65   $132.60  
  Purchase #3 $112.50   12.570%   $126.6413   $126.64   $126.65   $126.60  
  Purchase #4 $173.40   7.566%   $186.5194   $186.52   $186.50   $186.50  
  Purchase #5 $142.46   5.548%   $150.3637   $150.36   $150.35   $150.40  
  Purchase #6 $188.86   6.634%   $201.389   $201.39   $201.40   $201.40  
  Purchase #7 $215.93   3.797%   $224.1289   $224.13   $224.15   $224.10  
  7 purchase totals = $984.60       $1,059.2922   $1,059.29   $1,059.30   $1,059.20