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 $68.96   7.293%   $73.9893   $73.99   $74.00   $74.00  
  Purchase #2 $215.86   9.471%   $236.3041   $236.30   $236.30   $236.30  
  Purchase #3 $88.73   11.609%   $99.0307   $99.03   $99.05   $99.00  
  Purchase #4 $168.50   13.459%   $191.1784   $191.18   $191.20   $191.20  
  Purchase #5 $60.99   6.790%   $65.1312   $65.13   $65.15   $65.10  
  Purchase #6 $55.75   5.386%   $58.7527   $58.75   $58.75   $58.80  
  Purchase #7 $53.25   8.864%   $57.9701   $57.97   $57.95   $58.00  
  7 purchase totals = $712.04       $782.3565   $782.35   $782.40   $782.40