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 $41.59   10.585%   $45.9923   $45.99   $46.00   $46.00  
  Purchase #2 $154.94   8.201%   $167.6466   $167.65   $167.65   $167.60  
  Purchase #3 $217.95   13.502%   $247.3776   $247.38   $247.40   $247.40  
  Purchase #4 $117.29   4.518%   $122.5892   $122.59   $122.60   $122.60  
  Purchase #5 $21.98   5.676%   $23.2276   $23.23   $23.25   $23.20  
  Purchase #6 $137.73   9.653%   $151.0251   $151.03   $151.05   $151.00  
  Purchase #7 $163.47   7.457%   $175.66   $175.66   $175.65   $175.70  
  7 purchase totals = $854.95       $933.5184   $933.53   $933.60   $933.50