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 $62.94   3.244%   $64.9818   $64.98   $65.00   $65.00  
  Purchase #2 $87.74   5.582%   $92.6376   $92.64   $92.65   $92.60  
  Purchase #3 $185.28   10.422%   $204.5899   $204.59   $204.60   $204.60  
  Purchase #4 $100.37   9.528%   $109.9333   $109.93   $109.95   $109.90  
  Purchase #5 $174.37   7.785%   $187.9447   $187.94   $187.95   $187.90  
  Purchase #6 $222.55   3.133%   $229.5225   $229.52   $229.50   $229.50  
  Purchase #7 $210.88   4.741%   $220.8778   $220.88   $220.90   $220.90  
  7 purchase totals = $1,044.13       $1,110.4876   $1,110.48   $1,110.55   $1,110.40