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 $169.59   8.507%   $184.017   $184.02   $184.00   $184.00  
  Purchase #2 $109.43   7.274%   $117.3899   $117.39   $117.40   $117.40  
  Purchase #3 $90.33   9.232%   $98.6693   $98.67   $98.65   $98.70  
  Purchase #4 $110.70   8.181%   $119.7564   $119.76   $119.75   $119.80  
  Purchase #5 $190.89   4.748%   $199.9535   $199.95   $199.95   $200.00  
  Purchase #6 $162.48   11.483%   $181.1376   $181.14   $181.15   $181.10  
  Purchase #7 $213.86   3.814%   $222.0166   $222.02   $222.00   $222.00  
  7 purchase totals = $1,047.28       $1,122.9403   $1,122.95   $1,122.90   $1,123.00