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 $60.68   13.791%   $69.0484   $69.05   $69.05   $69.00  
  Purchase #2 $203.95   5.107%   $214.3657   $214.37   $214.35   $214.40  
  Purchase #3 $29.29   7.260%   $31.4165   $31.42   $31.40   $31.40  
  Purchase #4 $201.96   12.154%   $226.5062   $226.51   $226.50   $226.50  
  Purchase #5 $137.51   8.595%   $149.329   $149.33   $149.35   $149.30  
  Purchase #6 $97.83   6.642%   $104.3279   $104.33   $104.35   $104.30  
  Purchase #7 $90.71   7.261%   $97.2965   $97.30   $97.30   $97.30  
  7 purchase totals = $821.93       $892.2902   $892.31   $892.30   $892.20