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 $62.39   4.753%   $65.3554   $65.36   $65.35   $65.40  
  Purchase #2 $104.48   13.182%   $118.2526   $118.25   $118.25   $118.30  
  Purchase #3 $98.68   8.333%   $106.903   $106.90   $106.90   $106.90  
  Purchase #4 $193.39   5.112%   $203.2761   $203.28   $203.30   $203.30  
  Purchase #5 $116.99   10.618%   $129.412   $129.41   $129.40   $129.40  
  Purchase #6 $5.73   13.832%   $6.5226   $6.52   $6.50   $6.50  
  Purchase #7 $90.64   5.257%   $95.4049   $95.40   $95.40   $95.40  
  7 purchase totals = $672.30       $725.1266   $725.12   $725.10   $725.20