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 $196.50   5.363%   $207.0383   $207.04   $207.05   $207.00  
  Purchase #2 $76.55   8.753%   $83.2504   $83.25   $83.25   $83.30  
  Purchase #3 $247.26   11.188%   $274.9234   $274.92   $274.90   $274.90  
  Purchase #4 $116.91   13.677%   $132.8998   $132.90   $132.90   $132.90  
  Purchase #5 $8.76   11.108%   $9.7331   $9.73   $9.75   $9.70  
  Purchase #6 $225.59   4.350%   $235.4032   $235.40   $235.40   $235.40  
  Purchase #7 $64.46   9.444%   $70.5476   $70.55   $70.55   $70.50  
  7 purchase totals = $936.03       $1,013.7958   $1,013.79   $1,013.80   $1,013.70