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 $69.34   7.126%   $74.2812   $74.28   $74.30   $74.30  
  Purchase #2 $156.73   12.486%   $176.2993   $176.30   $176.30   $176.30  
  Purchase #3 $104.95   6.508%   $111.7801   $111.78   $111.80   $111.80  
  Purchase #4 $118.27   5.372%   $124.6235   $124.62   $124.60   $124.60  
  Purchase #5 $213.25   4.624%   $223.1107   $223.11   $223.10   $223.10  
  Purchase #6 $116.97   4.484%   $122.2149   $122.21   $122.20   $122.20  
  Purchase #7 $107.97   13.140%   $122.1573   $122.16   $122.15   $122.20  
  7 purchase totals = $887.48       $954.4670   $954.46   $954.45   $954.50