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 $86.41   8.806%   $94.0193   $94.02   $94.00   $94.00  
  Purchase #2 $194.87   5.254%   $205.1085   $205.11   $205.10   $205.10  
  Purchase #3 $53.85   8.676%   $58.522   $58.52   $58.50   $58.50  
  Purchase #4 $35.29   11.708%   $39.4218   $39.42   $39.40   $39.40  
  Purchase #5 $61.95   4.680%   $64.8493   $64.85   $64.85   $64.80  
  Purchase #6 $199.60   3.297%   $206.1808   $206.18   $206.20   $206.20  
  Purchase #7 $27.53   10.327%   $30.373   $30.37   $30.35   $30.40  
  7 purchase totals = $659.50       $698.4747   $698.47   $698.40   $698.40