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 $44.95   5.630%   $47.4807   $47.48   $47.50   $47.50  
  Purchase #2 $68.98   5.841%   $73.0091   $73.01   $73.00   $73.00  
  Purchase #3 $107.59   10.265%   $118.6341   $118.63   $118.65   $118.60  
  Purchase #4 $187.84   4.868%   $196.9841   $196.98   $197.00   $197.00  
  Purchase #5 $137.59   3.133%   $141.9007   $141.90   $141.90   $141.90  
  Purchase #6 $8.74   12.292%   $9.8143   $9.81   $9.80   $9.80  
  Purchase #7 $198.66   7.512%   $213.5833   $213.58   $213.60   $213.60  
  7 purchase totals = $754.35       $801.4063   $801.39   $801.45   $801.40