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 $44.83   4.188%   $46.7075   $46.71   $46.70   $46.70  
  Purchase #2 $116.60   7.621%   $125.4861   $125.49   $125.50   $125.50  
  Purchase #3 $243.44   13.739%   $276.8862   $276.89   $276.90   $276.90  
  Purchase #4 $153.55   10.314%   $169.3871   $169.39   $169.40   $169.40  
  Purchase #5 $77.79   12.279%   $87.3418   $87.34   $87.35   $87.30  
  Purchase #6 $23.42   6.130%   $24.8556   $24.86   $24.85   $24.90  
  Purchase #7 $131.62   10.299%   $145.1755   $145.18   $145.20   $145.20  
  7 purchase totals = $791.25       $875.8398   $875.86   $875.90   $875.90