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 $72.73   3.174%   $75.0385   $75.04   $75.05   $75.00  
  Purchase #2 $165.49   10.648%   $183.1114   $183.11   $183.10   $183.10  
  Purchase #3 $59.49   12.752%   $67.0762   $67.08   $67.10   $67.10  
  Purchase #4 $221.48   5.251%   $233.1099   $233.11   $233.10   $233.10  
  Purchase #5 $49.80   4.460%   $52.0211   $52.02   $52.00   $52.00  
  Purchase #6 $236.81   3.605%   $245.347   $245.35   $245.35   $245.30  
  Purchase #7 $151.71   4.545%   $158.6052   $158.61   $158.60   $158.60  
  7 purchase totals = $957.51       $1,014.3093   $1,014.32   $1,014.30   $1,014.20