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 $217.74   8.821%   $236.9468   $236.95   $236.95   $236.90  
  Purchase #2 $95.36   4.545%   $99.6941   $99.69   $99.70   $99.70  
  Purchase #3 $129.97   8.788%   $141.3918   $141.39   $141.40   $141.40  
  Purchase #4 $148.60   3.489%   $153.7847   $153.78   $153.80   $153.80  
  Purchase #5 $124.30   8.614%   $135.0072   $135.01   $135.00   $135.00  
  Purchase #6 $172.67   12.568%   $194.3712   $194.37   $194.35   $194.40  
  Purchase #7 $144.89   5.678%   $153.1169   $153.12   $153.10   $153.10  
  7 purchase totals = $1,033.53       $1,114.3127   $1,114.31   $1,114.30   $1,114.30