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 $213.78   8.768%   $232.5242   $232.52   $232.50   $232.50  
  Purchase #2 $215.52   13.327%   $244.2424   $244.24   $244.25   $244.20  
  Purchase #3 $176.63   10.387%   $194.9766   $194.98   $195.00   $195.00  
  Purchase #4 $214.73   8.688%   $233.3857   $233.39   $233.40   $233.40  
  Purchase #5 $201.25   9.296%   $219.9582   $219.96   $219.95   $220.00  
  Purchase #6 $112.79   9.506%   $123.5118   $123.51   $123.50   $123.50  
  Purchase #7 $162.55   8.311%   $176.0595   $176.06   $176.05   $176.10  
  7 purchase totals = $1,297.25       $1,424.6584   $1,424.66   $1,424.65   $1,424.70