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 $85.42   11.363%   $95.1263   $95.13   $95.15   $95.10  
  Purchase #2 $114.67   10.167%   $126.3285   $126.33   $126.35   $126.30  
  Purchase #3 $22.46   9.216%   $24.5299   $24.53   $24.55   $24.50  
  Purchase #4 $13.98   13.791%   $15.908   $15.91   $15.90   $15.90  
  Purchase #5 $128.88   6.140%   $136.7932   $136.79   $136.80   $136.80  
  Purchase #6 $128.53   11.741%   $143.6207   $143.62   $143.60   $143.60  
  Purchase #7 $203.32   8.649%   $220.9051   $220.91   $220.90   $220.90  
  7 purchase totals = $697.26       $763.2117   $763.22   $763.25   $763.10