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 $118.76   7.486%   $127.6504   $127.65   $127.65   $127.70  
  Purchase #2 $233.73   4.473%   $244.1847   $244.18   $244.20   $244.20  
  Purchase #3 $53.36   8.115%   $57.6902   $57.69   $57.70   $57.70  
  Purchase #4 $221.38   9.206%   $241.7602   $241.76   $241.75   $241.80  
  Purchase #5 $219.32   3.421%   $226.8229   $226.82   $226.80   $226.80  
  Purchase #6 $175.33   5.380%   $184.7628   $184.76   $184.75   $184.80  
  Purchase #7 $129.88   11.479%   $144.7889   $144.79   $144.80   $144.80  
  7 purchase totals = $1,151.76       $1,227.6601   $1,227.65   $1,227.65   $1,227.80