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 $97.63   11.137%   $108.5031   $108.50   $108.50   $108.50  
  Purchase #2 $39.40   9.414%   $43.1091   $43.11   $43.10   $43.10  
  Purchase #3 $97.44   5.277%   $102.5819   $102.58   $102.60   $102.60  
  Purchase #4 $154.72   9.252%   $169.0347   $169.03   $169.05   $169.00  
  Purchase #5 $174.42   6.199%   $185.2323   $185.23   $185.25   $185.20  
  Purchase #6 $205.39   3.625%   $212.8354   $212.84   $212.85   $212.80  
  Purchase #7 $127.72   4.365%   $133.295   $133.30   $133.30   $133.30  
  7 purchase totals = $896.72       $954.5915   $954.59   $954.65   $954.50