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 $236.51   3.397%   $244.5442   $244.54   $244.55   $244.50  
  Purchase #2 $195.60   10.760%   $216.6466   $216.65   $216.65   $216.60  
  Purchase #3 $241.48   11.767%   $269.895   $269.90   $269.90   $269.90  
  Purchase #4 $202.37   7.369%   $217.2826   $217.28   $217.30   $217.30  
  Purchase #5 $143.79   4.673%   $150.5093   $150.51   $150.50   $150.50  
  Purchase #6 $187.88   3.670%   $194.7752   $194.78   $194.80   $194.80  
  Purchase #7 $181.71   11.702%   $202.9737   $202.97   $202.95   $203.00  
  7 purchase totals = $1,389.34       $1,496.6266   $1,496.63   $1,496.65   $1,496.60