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 $212.85   11.491%   $237.3086   $237.31   $237.30   $237.30  
  Purchase #2 $104.52   3.202%   $107.8667   $107.87   $107.85   $107.90  
  Purchase #3 $14.75   3.458%   $15.2601   $15.26   $15.25   $15.30  
  Purchase #4 $92.43   5.672%   $97.6726   $97.67   $97.65   $97.70  
  Purchase #5 $69.28   3.765%   $71.8884   $71.89   $71.90   $71.90  
  Purchase #6 $119.70   7.412%   $128.5722   $128.57   $128.55   $128.60  
  Purchase #7 $79.83   6.133%   $84.726   $84.73   $84.75   $84.70  
  7 purchase totals = $693.36       $743.2946   $743.30   $743.25   $743.40