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 $105.78   8.114%   $114.363   $114.36   $114.35   $114.40  
  Purchase #2 $167.65   3.343%   $173.2545   $173.25   $173.25   $173.30  
  Purchase #3 $124.81   12.286%   $140.1442   $140.14   $140.15   $140.10  
  Purchase #4 $95.99   5.184%   $100.9661   $100.97   $100.95   $101.00  
  Purchase #5 $108.84   13.507%   $123.541   $123.54   $123.55   $123.50  
  Purchase #6 $53.74   12.365%   $60.385   $60.39   $60.40   $60.40  
  Purchase #7 $219.52   8.600%   $238.3987   $238.40   $238.40   $238.40  
  7 purchase totals = $876.33       $951.0525   $951.05   $951.05   $951.10