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 $43.98   6.775%   $46.9596   $46.96   $46.95   $47.00  
  Purchase #2 $114.87   5.110%   $120.7399   $120.74   $120.75   $120.70  
  Purchase #3 $6.63   4.220%   $6.9098   $6.91   $6.90   $6.90  
  Purchase #4 $103.84   5.734%   $109.7942   $109.79   $109.80   $109.80  
  Purchase #5 $114.99   10.686%   $127.2778   $127.28   $127.30   $127.30  
  Purchase #6 $129.35   10.436%   $142.849   $142.85   $142.85   $142.80  
  Purchase #7 $150.59   5.596%   $159.017   $159.02   $159.00   $159.00  
  7 purchase totals = $664.25       $713.5473   $713.55   $713.55   $713.50