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 $91.74   3.104%   $94.5876   $94.59   $94.60   $94.60  
  Purchase #2 $59.95   3.617%   $62.1184   $62.12   $62.10   $62.10  
  Purchase #3 $83.31   10.477%   $92.0384   $92.04   $92.05   $92.00  
  Purchase #4 $54.37   11.570%   $60.6606   $60.66   $60.65   $60.70  
  Purchase #5 $126.31   3.293%   $130.4694   $130.47   $130.45   $130.50  
  Purchase #6 $134.98   9.793%   $148.1986   $148.20   $148.20   $148.20  
  Purchase #7 $172.65   6.729%   $184.2676   $184.27   $184.25   $184.30  
  7 purchase totals = $723.31       $772.3406   $772.35   $772.30   $772.40