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 $41.36   13.549%   $46.9639   $46.96   $46.95   $47.00  
  Purchase #2 $113.88   5.633%   $120.2949   $120.29   $120.30   $120.30  
  Purchase #3 $117.37   11.543%   $130.918   $130.92   $130.90   $130.90  
  Purchase #4 $131.28   4.675%   $137.4173   $137.42   $137.40   $137.40  
  Purchase #5 $213.64   7.458%   $229.5733   $229.57   $229.55   $229.60  
  Purchase #6 $230.58   10.425%   $254.618   $254.62   $254.60   $254.60  
  Purchase #7 $202.56   13.496%   $229.8975   $229.90   $229.90   $229.90  
  7 purchase totals = $1,050.67       $1,149.6829   $1,149.68   $1,149.60   $1,149.70