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 $227.56   7.644%   $244.9547   $244.95   $244.95   $245.00  
  Purchase #2 $129.78   8.211%   $140.4362   $140.44   $140.45   $140.40  
  Purchase #3 $58.38   11.319%   $64.988   $64.99   $65.00   $65.00  
  Purchase #4 $44.53   7.679%   $47.9495   $47.95   $47.95   $47.90  
  Purchase #5 $103.79   13.645%   $117.9521   $117.95   $117.95   $118.00  
  Purchase #6 $192.75   13.409%   $218.5958   $218.60   $218.60   $218.60  
  Purchase #7 $49.59   12.612%   $55.8443   $55.84   $55.85   $55.80  
  7 purchase totals = $806.38       $890.7206   $890.72   $890.75   $890.70