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 $95.29   6.796%   $101.7659   $101.77   $101.75   $101.80  
  Purchase #2 $79.93   11.131%   $88.827   $88.83   $88.85   $88.80  
  Purchase #3 $169.91   4.694%   $177.8856   $177.89   $177.90   $177.90  
  Purchase #4 $84.64   8.319%   $91.6812   $91.68   $91.70   $91.70  
  Purchase #5 $58.25   13.371%   $66.0386   $66.04   $66.05   $66.00  
  Purchase #6 $215.30   4.663%   $225.3394   $225.34   $225.35   $225.30  
  Purchase #7 $5.60   5.491%   $5.9075   $5.91   $5.90   $5.90  
  7 purchase totals = $708.92       $757.4452   $757.46   $757.50   $757.40