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 $69.69   8.422%   $75.5593   $75.56   $75.55   $75.60  
  Purchase #2 $219.93   11.128%   $244.4038   $244.40   $244.40   $244.40  
  Purchase #3 $46.86   5.299%   $49.3431   $49.34   $49.35   $49.30  
  Purchase #4 $152.70   10.719%   $169.0679   $169.07   $169.05   $169.10  
  Purchase #5 $120.82   4.772%   $126.5855   $126.59   $126.60   $126.60  
  Purchase #6 $220.46   9.758%   $241.9725   $241.97   $241.95   $242.00  
  Purchase #7 $231.61   6.764%   $247.2761   $247.28   $247.30   $247.30  
  7 purchase totals = $1,062.07       $1,154.2082   $1,154.21   $1,154.20   $1,154.30