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 $62.46   7.316%   $67.0296   $67.03   $67.05   $67.00  
  Purchase #2 $182.63   13.471%   $207.2321   $207.23   $207.25   $207.20  
  Purchase #3 $218.94   8.405%   $237.3419   $237.34   $237.35   $237.30  
  Purchase #4 $223.96   3.747%   $232.3518   $232.35   $232.35   $232.40  
  Purchase #5 $151.97   4.575%   $158.9226   $158.92   $158.90   $158.90  
  Purchase #6 $173.31   6.308%   $184.2424   $184.24   $184.25   $184.20  
  Purchase #7 $98.70   4.542%   $103.183   $103.18   $103.20   $103.20  
  7 purchase totals = $1,111.97       $1,190.3034   $1,190.29   $1,190.35   $1,190.20