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 $147.67   13.510%   $167.6202   $167.62   $167.60   $167.60  
  Purchase #2 $241.90   4.461%   $252.6912   $252.69   $252.70   $252.70  
  Purchase #3 $232.87   4.851%   $244.1665   $244.17   $244.15   $244.20  
  Purchase #4 $21.83   12.687%   $24.5996   $24.60   $24.60   $24.60  
  Purchase #5 $111.79   3.343%   $115.5271   $115.53   $115.55   $115.50  
  Purchase #6 $246.65   11.362%   $274.6744   $274.67   $274.65   $274.70  
  Purchase #7 $119.96   8.330%   $129.9527   $129.95   $129.95   $130.00  
  7 purchase totals = $1,122.67       $1,209.2317   $1,209.23   $1,209.20   $1,209.30