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 $96.30   11.387%   $107.2657   $107.27   $107.25   $107.30  
  Purchase #2 $146.37   11.805%   $163.649   $163.65   $163.65   $163.60  
  Purchase #3 $63.77   7.124%   $68.313   $68.31   $68.30   $68.30  
  Purchase #4 $214.41   11.114%   $238.2395   $238.24   $238.25   $238.20  
  Purchase #5 $175.80   5.381%   $185.2598   $185.26   $185.25   $185.30  
  Purchase #6 $210.36   9.829%   $231.0363   $231.04   $231.05   $231.00  
  Purchase #7 $197.93   3.361%   $204.5824   $204.58   $204.60   $204.60  
  7 purchase totals = $1,104.94       $1,198.3457   $1,198.35   $1,198.35   $1,198.30