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 $244.54   5.369%   $257.6694   $257.67   $257.65   $257.70  
  Purchase #2 $196.87   13.342%   $223.1364   $223.14   $223.15   $223.10  
  Purchase #3 $84.73   12.650%   $95.4483   $95.45   $95.45   $95.40  
  Purchase #4 $204.94   6.134%   $217.511   $217.51   $217.50   $217.50  
  Purchase #5 $127.25   4.420%   $132.8745   $132.87   $132.85   $132.90  
  Purchase #6 $86.32   12.121%   $96.7828   $96.78   $96.80   $96.80  
  Purchase #7 $8.56   11.792%   $9.5694   $9.57   $9.55   $9.60  
  7 purchase totals = $953.21       $1,032.9918   $1,032.99   $1,032.95   $1,033.00