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 $84.79   13.471%   $96.2121   $96.21   $96.20   $96.20  
  Purchase #2 $119.69   5.552%   $126.3352   $126.34   $126.35   $126.30  
  Purchase #3 $172.47   5.482%   $181.9248   $181.92   $181.90   $181.90  
  Purchase #4 $205.68   3.567%   $213.0166   $213.02   $213.00   $213.00  
  Purchase #5 $214.36   6.868%   $229.0822   $229.08   $229.10   $229.10  
  Purchase #6 $149.86   4.248%   $156.2261   $156.23   $156.25   $156.20  
  Purchase #7 $183.98   4.343%   $191.9703   $191.97   $191.95   $192.00  
  7 purchase totals = $1,130.83       $1,194.7673   $1,194.77   $1,194.75   $1,194.70