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 $173.34   12.491%   $194.9919   $194.99   $195.00   $195.00  
  Purchase #2 $157.40   6.336%   $167.3729   $167.37   $167.35   $167.40  
  Purchase #3 $47.83   13.286%   $54.1847   $54.18   $54.20   $54.20  
  Purchase #4 $40.89   11.277%   $45.5012   $45.50   $45.50   $45.50  
  Purchase #5 $249.74   4.791%   $261.705   $261.71   $261.70   $261.70  
  Purchase #6 $178.44   4.541%   $186.543   $186.54   $186.55   $186.50  
  Purchase #7 $186.52   4.165%   $194.2886   $194.29   $194.30   $194.30  
  7 purchase totals = $1,034.16       $1,104.5873   $1,104.58   $1,104.60   $1,104.60