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 $176.72   10.511%   $195.295   $195.30   $195.30   $195.30  
  Purchase #2 $12.27   8.309%   $13.2895   $13.29   $13.30   $13.30  
  Purchase #3 $131.53   13.140%   $148.813   $148.81   $148.80   $148.80  
  Purchase #4 $142.58   8.559%   $154.7834   $154.78   $154.80   $154.80  
  Purchase #5 $121.87   9.364%   $133.2819   $133.28   $133.30   $133.30  
  Purchase #6 $216.74   13.790%   $246.6284   $246.63   $246.65   $246.60  
  Purchase #7 $208.35   5.117%   $219.0113   $219.01   $219.00   $219.00  
  7 purchase totals = $1,010.06       $1,111.1025   $1,111.10   $1,111.15   $1,111.10