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 $114.64   9.789%   $125.8621   $125.86   $125.85   $125.90  
  Purchase #2 $197.69   5.820%   $209.1956   $209.20   $209.20   $209.20  
  Purchase #3 $137.39   12.831%   $155.0185   $155.02   $155.00   $155.00  
  Purchase #4 $87.74   13.394%   $99.4919   $99.49   $99.50   $99.50  
  Purchase #5 $229.69   4.823%   $240.7679   $240.77   $240.75   $240.80  
  Purchase #6 $169.43   3.862%   $175.9734   $175.97   $175.95   $176.00  
  Purchase #7 $48.28   13.176%   $54.6414   $54.64   $54.65   $54.60  
  7 purchase totals = $984.86       $1,060.9508   $1,060.95   $1,060.90   $1,061.00