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 $225.46   5.348%   $237.5176   $237.52   $237.50   $237.50  
  Purchase #2 $156.33   4.108%   $162.752   $162.75   $162.75   $162.80  
  Purchase #3 $61.99   11.268%   $68.975   $68.98   $69.00   $69.00  
  Purchase #4 $215.40   5.608%   $227.4796   $227.48   $227.50   $227.50  
  Purchase #5 $125.95   13.515%   $142.9721   $142.97   $142.95   $143.00  
  Purchase #6 $34.78   7.466%   $37.3767   $37.38   $37.40   $37.40  
  Purchase #7 $151.99   13.117%   $171.9265   $171.93   $171.95   $171.90  
  7 purchase totals = $971.90       $1,048.9995   $1,049.01   $1,049.05   $1,049.10