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 $59.34   11.137%   $65.9487   $65.95   $65.95   $65.90  
  Purchase #2 $90.86   5.476%   $95.8355   $95.84   $95.85   $95.80  
  Purchase #3 $96.77   7.485%   $104.0132   $104.01   $104.00   $104.00  
  Purchase #4 $36.38   5.285%   $38.3027   $38.30   $38.30   $38.30  
  Purchase #5 $181.48   5.435%   $191.3434   $191.34   $191.35   $191.30  
  Purchase #6 $211.74   10.403%   $233.7673   $233.77   $233.75   $233.80  
  Purchase #7 $69.47   10.499%   $76.7637   $76.76   $76.75   $76.80  
  7 purchase totals = $746.04       $805.9745   $805.97   $805.95   $805.90