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 $148.51   3.257%   $153.347   $153.35   $153.35   $153.30  
  Purchase #2 $57.28   3.644%   $59.3673   $59.37   $59.35   $59.40  
  Purchase #3 $63.30   7.649%   $68.1418   $68.14   $68.15   $68.10  
  Purchase #4 $114.66   4.778%   $120.1385   $120.14   $120.15   $120.10  
  Purchase #5 $48.43   11.768%   $54.1292   $54.13   $54.15   $54.10  
  Purchase #6 $26.86   6.420%   $28.5844   $28.58   $28.60   $28.60  
  Purchase #7 $213.55   11.572%   $238.262   $238.26   $238.25   $238.30  
  7 purchase totals = $672.59       $721.9702   $721.97   $722.00   $721.90