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 $69.37   6.316%   $73.7514   $73.75   $73.75   $73.80  
  Purchase #2 $99.92   7.388%   $107.3021   $107.30   $107.30   $107.30  
  Purchase #3 $108.34   9.636%   $118.7796   $118.78   $118.80   $118.80  
  Purchase #4 $228.59   3.385%   $236.3278   $236.33   $236.35   $236.30  
  Purchase #5 $185.76   5.343%   $195.6852   $195.69   $195.70   $195.70  
  Purchase #6 $172.55   6.297%   $183.4155   $183.42   $183.40   $183.40  
  Purchase #7 $168.95   10.789%   $187.178   $187.18   $187.20   $187.20  
  7 purchase totals = $1,033.48       $1,102.4396   $1,102.45   $1,102.50   $1,102.50