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 $239.68   11.803%   $267.9694   $267.97   $267.95   $268.00  
  Purchase #2 $103.70   9.512%   $113.5639   $113.56   $113.55   $113.60  
  Purchase #3 $145.68   7.169%   $156.1238   $156.12   $156.10   $156.10  
  Purchase #4 $209.69   8.541%   $227.5996   $227.60   $227.60   $227.60  
  Purchase #5 $189.53   8.228%   $205.1245   $205.12   $205.10   $205.10  
  Purchase #6 $232.69   11.869%   $260.308   $260.31   $260.30   $260.30  
  Purchase #7 $204.40   13.626%   $232.2515   $232.25   $232.25   $232.30  
  7 purchase totals = $1,325.37       $1,462.9407   $1,462.93   $1,462.85   $1,463.00