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 $82.89   13.238%   $93.863   $93.86   $93.85   $93.90  
  Purchase #2 $42.31   3.156%   $43.6453   $43.65   $43.65   $43.60  
  Purchase #3 $97.99   4.574%   $102.4721   $102.47   $102.45   $102.50  
  Purchase #4 $215.84   13.428%   $244.823   $244.82   $244.80   $244.80  
  Purchase #5 $108.47   6.704%   $115.7418   $115.74   $115.75   $115.70  
  Purchase #6 $93.93   10.689%   $103.9702   $103.97   $103.95   $104.00  
  Purchase #7 $33.55   8.644%   $36.4501   $36.45   $36.45   $36.50  
  7 purchase totals = $674.98       $740.9655   $740.96   $740.90   $741.00