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 $43.27   9.613%   $47.4295   $47.43   $47.45   $47.40  
  Purchase #2 $236.82   6.211%   $251.5289   $251.53   $251.55   $251.50  
  Purchase #3 $169.72   3.810%   $176.1863   $176.19   $176.20   $176.20  
  Purchase #4 $199.60   8.250%   $216.067   $216.07   $216.05   $216.10  
  Purchase #5 $53.34   4.742%   $55.8694   $55.87   $55.85   $55.90  
  Purchase #6 $167.68   10.742%   $185.6922   $185.69   $185.70   $185.70  
  Purchase #7 $214.76   5.840%   $227.302   $227.30   $227.30   $227.30  
  7 purchase totals = $1,085.19       $1,160.0753   $1,160.08   $1,160.10   $1,160.10