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 $41.29   5.299%   $43.478   $43.48   $43.50   $43.50  
  Purchase #2 $11.90   6.444%   $12.6668   $12.67   $12.65   $12.70  
  Purchase #3 $73.36   11.603%   $81.872   $81.87   $81.85   $81.90  
  Purchase #4 $87.87   8.505%   $95.3433   $95.34   $95.35   $95.30  
  Purchase #5 $232.62   5.312%   $244.9768   $244.98   $245.00   $245.00  
  Purchase #6 $104.51   13.843%   $118.9773   $118.98   $119.00   $119.00  
  Purchase #7 $140.74   4.353%   $146.8664   $146.87   $146.85   $146.90  
  7 purchase totals = $692.29       $744.1806   $744.19   $744.20   $744.30