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 $176.41   11.546%   $196.7783   $196.78   $196.80   $196.80  
  Purchase #2 $118.29   12.647%   $133.2501   $133.25   $133.25   $133.30  
  Purchase #3 $194.30   7.766%   $209.3893   $209.39   $209.40   $209.40  
  Purchase #4 $195.58   3.499%   $202.4233   $202.42   $202.40   $202.40  
  Purchase #5 $45.43   4.834%   $47.6261   $47.63   $47.65   $47.60  
  Purchase #6 $43.57   7.568%   $46.8674   $46.87   $46.85   $46.90  
  Purchase #7 $184.79   7.407%   $198.4774   $198.48   $198.50   $198.50  
  7 purchase totals = $958.37       $1,034.8119   $1,034.82   $1,034.85   $1,034.90