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 $43.38   8.425%   $47.0348   $47.03   $47.05   $47.00  
  Purchase #2 $59.25   10.440%   $65.4357   $65.44   $65.45   $65.40  
  Purchase #3 $97.76   4.549%   $102.2071   $102.21   $102.20   $102.20  
  Purchase #4 $140.82   4.607%   $147.3076   $147.31   $147.30   $147.30  
  Purchase #5 $126.33   4.337%   $131.8089   $131.81   $131.80   $131.80  
  Purchase #6 $128.53   3.264%   $132.7252   $132.73   $132.75   $132.70  
  Purchase #7 $241.74   10.643%   $267.4684   $267.47   $267.45   $267.50  
  7 purchase totals = $837.81       $893.9877   $894.00   $894.00   $893.90