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 $43.25   8.293%   $46.8367   $46.84   $46.85   $46.80  
  Purchase #2 $204.95   5.722%   $216.6772   $216.68   $216.70   $216.70  
  Purchase #3 $96.31   13.848%   $109.647   $109.65   $109.65   $109.60  
  Purchase #4 $199.84   3.332%   $206.4987   $206.50   $206.50   $206.50  
  Purchase #5 $98.41   3.617%   $101.9695   $101.97   $101.95   $102.00  
  Purchase #6 $202.80   7.297%   $217.5983   $217.60   $217.60   $217.60  
  Purchase #7 $114.74   12.511%   $129.0951   $129.10   $129.10   $129.10  
  7 purchase totals = $960.30       $1,028.3225   $1,028.34   $1,028.35   $1,028.30