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 $60.74   4.823%   $63.6695   $63.67   $63.65   $63.70  
  Purchase #2 $168.29   6.822%   $179.7707   $179.77   $179.75   $179.80  
  Purchase #3 $88.85   6.773%   $94.8678   $94.87   $94.85   $94.90  
  Purchase #4 $247.30   3.473%   $255.8887   $255.89   $255.90   $255.90  
  Purchase #5 $15.74   7.727%   $16.9562   $16.96   $16.95   $17.00  
  Purchase #6 $117.33   8.775%   $127.6257   $127.63   $127.65   $127.60  
  Purchase #7 $139.62   6.401%   $148.5571   $148.56   $148.55   $148.60  
  7 purchase totals = $837.87       $887.3357   $887.35   $887.30   $887.50