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 $85.37   10.725%   $94.5259   $94.53   $94.55   $94.50  
  Purchase #2 $237.86   4.656%   $248.9348   $248.93   $248.95   $248.90  
  Purchase #3 $55.92   8.841%   $60.8639   $60.86   $60.85   $60.90  
  Purchase #4 $78.41   11.483%   $87.4138   $87.41   $87.40   $87.40  
  Purchase #5 $247.93   11.298%   $275.9411   $275.94   $275.95   $275.90  
  Purchase #6 $118.49   7.733%   $127.6528   $127.65   $127.65   $127.70  
  Purchase #7 $137.49   11.761%   $153.6602   $153.66   $153.65   $153.70  
  7 purchase totals = $961.47       $1,048.9925   $1,048.98   $1,049.00   $1,049.00