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 $84.26   9.546%   $92.3035   $92.30   $92.30   $92.30  
  Purchase #2 $217.30   8.859%   $236.5506   $236.55   $236.55   $236.60  
  Purchase #3 $159.96   9.565%   $175.2602   $175.26   $175.25   $175.30  
  Purchase #4 $56.31   7.243%   $60.3885   $60.39   $60.40   $60.40  
  Purchase #5 $95.42   4.583%   $99.7931   $99.79   $99.80   $99.80  
  Purchase #6 $36.40   8.467%   $39.482   $39.48   $39.50   $39.50  
  Purchase #7 $236.73   5.610%   $250.0106   $250.01   $250.00   $250.00  
  7 purchase totals = $886.38       $953.7885   $953.78   $953.80   $953.90