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 $84.70   11.772%   $94.6709   $94.67   $94.65   $94.70  
  Purchase #2 $233.89   5.135%   $245.9003   $245.90   $245.90   $245.90  
  Purchase #3 $121.71   4.279%   $126.918   $126.92   $126.90   $126.90  
  Purchase #4 $79.74   10.554%   $88.1558   $88.16   $88.15   $88.20  
  Purchase #5 $124.61   11.262%   $138.6436   $138.64   $138.65   $138.60  
  Purchase #6 $9.47   9.448%   $10.3647   $10.36   $10.35   $10.40  
  Purchase #7 $169.49   11.224%   $188.5136   $188.51   $188.50   $188.50  
  7 purchase totals = $823.61       $893.1669   $893.16   $893.10   $893.20