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 $88.38   9.749%   $96.9962   $97.00   $97.00   $97.00  
  Purchase #2 $69.99   5.382%   $73.7569   $73.76   $73.75   $73.80  
  Purchase #3 $70.33   9.761%   $77.1949   $77.19   $77.20   $77.20  
  Purchase #4 $30.84   9.721%   $33.838   $33.84   $33.85   $33.80  
  Purchase #5 $129.37   4.540%   $135.2434   $135.24   $135.25   $135.20  
  Purchase #6 $180.34   6.809%   $192.6194   $192.62   $192.60   $192.60  
  Purchase #7 $110.70   5.796%   $117.1162   $117.12   $117.10   $117.10  
  7 purchase totals = $679.95       $726.7650   $726.77   $726.75   $726.70