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 $61.81   9.183%   $67.486   $67.49   $67.50   $67.50  
  Purchase #2 $48.81   4.439%   $50.9767   $50.98   $51.00   $51.00  
  Purchase #3 $153.98   13.505%   $174.775   $174.78   $174.80   $174.80  
  Purchase #4 $62.26   11.768%   $69.5868   $69.59   $69.60   $69.60  
  Purchase #5 $91.25   5.378%   $96.1574   $96.16   $96.15   $96.20  
  Purchase #6 $189.88   4.618%   $198.6487   $198.65   $198.65   $198.60  
  Purchase #7 $92.70   13.164%   $104.903   $104.90   $104.90   $104.90  
  7 purchase totals = $700.69       $762.5336   $762.55   $762.60   $762.60