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 $209.92   11.760%   $234.6066   $234.61   $234.60   $234.60  
  Purchase #2 $198.41   10.696%   $219.6319   $219.63   $219.65   $219.60  
  Purchase #3 $88.42   4.257%   $92.184   $92.18   $92.20   $92.20  
  Purchase #4 $195.73   4.346%   $204.2364   $204.24   $204.25   $204.20  
  Purchase #5 $158.89   3.244%   $164.0444   $164.04   $164.05   $164.00  
  Purchase #6 $8.55   4.753%   $8.9564   $8.96   $8.95   $9.00  
  Purchase #7 $207.92   11.666%   $232.1759   $232.18   $232.20   $232.20  
  7 purchase totals = $1,067.84       $1,155.8356   $1,155.84   $1,155.90   $1,155.80