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 $61.26   8.691%   $66.5841   $66.58   $66.60   $66.60  
  Purchase #2 $55.38   9.152%   $60.4484   $60.45   $60.45   $60.40  
  Purchase #3 $228.82   5.463%   $241.3204   $241.32   $241.30   $241.30  
  Purchase #4 $218.47   9.590%   $239.4213   $239.42   $239.40   $239.40  
  Purchase #5 $49.86   4.435%   $52.0713   $52.07   $52.05   $52.10  
  Purchase #6 $217.35   4.722%   $227.6133   $227.61   $227.60   $227.60  
  Purchase #7 $230.73   7.110%   $247.1349   $247.13   $247.15   $247.10  
  7 purchase totals = $1,061.87       $1,134.5937   $1,134.58   $1,134.55   $1,134.50