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 $200.63   6.687%   $214.0461   $214.05   $214.05   $214.00  
  Purchase #2 $94.64   13.849%   $107.7467   $107.75   $107.75   $107.70  
  Purchase #3 $181.58   7.562%   $195.3111   $195.31   $195.30   $195.30  
  Purchase #4 $91.32   7.576%   $98.2384   $98.24   $98.25   $98.20  
  Purchase #5 $37.92   10.734%   $41.9903   $41.99   $42.00   $42.00  
  Purchase #6 $58.93   9.658%   $64.6215   $64.62   $64.60   $64.60  
  Purchase #7 $236.29   3.542%   $244.6594   $244.66   $244.65   $244.70  
  7 purchase totals = $901.31       $966.6135   $966.62   $966.60   $966.50