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 $218.73   10.430%   $241.5435   $241.54   $241.55   $241.50  
  Purchase #2 $65.96   10.644%   $72.9808   $72.98   $73.00   $73.00  
  Purchase #3 $113.56   4.538%   $118.7134   $118.71   $118.70   $118.70  
  Purchase #4 $31.44   6.521%   $33.4902   $33.49   $33.50   $33.50  
  Purchase #5 $223.32   4.671%   $233.7513   $233.75   $233.75   $233.80  
  Purchase #6 $21.86   7.753%   $23.5548   $23.55   $23.55   $23.60  
  Purchase #7 $44.58   7.663%   $47.9962   $48.00   $48.00   $48.00  
  7 purchase totals = $719.45       $772.0302   $772.02   $772.05   $772.10