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 $211.29   10.148%   $232.7317   $232.73   $232.75   $232.70  
  Purchase #2 $94.32   8.644%   $102.473   $102.47   $102.45   $102.50  
  Purchase #3 $153.53   13.440%   $174.1644   $174.16   $174.15   $174.20  
  Purchase #4 $119.74   12.377%   $134.5602   $134.56   $134.55   $134.60  
  Purchase #5 $47.32   8.496%   $51.3403   $51.34   $51.35   $51.30  
  Purchase #6 $37.90   7.467%   $40.73   $40.73   $40.75   $40.70  
  Purchase #7 $117.68   11.367%   $131.0567   $131.06   $131.05   $131.10  
  7 purchase totals = $781.78       $867.0563   $867.05   $867.05   $867.10