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 $56.78   10.307%   $62.6323   $62.63   $62.65   $62.60  
  Purchase #2 $202.54   11.258%   $225.342   $225.34   $225.35   $225.30  
  Purchase #3 $109.56   9.736%   $120.2268   $120.23   $120.25   $120.20  
  Purchase #4 $206.29   3.288%   $213.0728   $213.07   $213.05   $213.10  
  Purchase #5 $195.98   9.593%   $214.7804   $214.78   $214.80   $214.80  
  Purchase #6 $50.34   12.732%   $56.7493   $56.75   $56.75   $56.70  
  Purchase #7 $247.81   4.571%   $259.1374   $259.14   $259.15   $259.10  
  7 purchase totals = $1,069.30       $1,151.9410   $1,151.94   $1,152.00   $1,151.80