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 $168.42   10.421%   $185.971   $185.97   $185.95   $186.00  
  Purchase #2 $233.98   12.736%   $263.7797   $263.78   $263.80   $263.80  
  Purchase #3 $59.82   3.600%   $61.9735   $61.97   $61.95   $62.00  
  Purchase #4 $30.99   9.403%   $33.904   $33.90   $33.90   $33.90  
  Purchase #5 $64.59   7.307%   $69.3096   $69.31   $69.30   $69.30  
  Purchase #6 $222.39   10.317%   $245.334   $245.33   $245.35   $245.30  
  Purchase #7 $121.26   3.155%   $125.0858   $125.09   $125.10   $125.10  
  7 purchase totals = $901.45       $985.3576   $985.35   $985.35   $985.40