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 $221.82   11.767%   $247.9216   $247.92   $247.90   $247.90  
  Purchase #2 $213.66   11.811%   $238.8954   $238.90   $238.90   $238.90  
  Purchase #3 $88.91   8.802%   $96.7359   $96.74   $96.75   $96.70  
  Purchase #4 $142.48   13.692%   $161.9884   $161.99   $162.00   $162.00  
  Purchase #5 $158.98   10.405%   $175.5219   $175.52   $175.50   $175.50  
  Purchase #6 $137.68   11.527%   $153.5504   $153.55   $153.55   $153.60  
  Purchase #7 $105.30   13.873%   $119.9083   $119.91   $119.90   $119.90  
  7 purchase totals = $1,068.83       $1,194.5219   $1,194.53   $1,194.50   $1,194.50