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 $211.99   11.201%   $235.735   $235.74   $235.75   $235.70  
  Purchase #2 $178.74   9.478%   $195.681   $195.68   $195.70   $195.70  
  Purchase #3 $169.40   5.771%   $179.1761   $179.18   $179.20   $179.20  
  Purchase #4 $51.60   9.189%   $56.3415   $56.34   $56.35   $56.30  
  Purchase #5 $248.76   8.280%   $269.3573   $269.36   $269.35   $269.40  
  Purchase #6 $116.69   13.377%   $132.2996   $132.30   $132.30   $132.30  
  Purchase #7 $202.56   5.739%   $214.1849   $214.18   $214.20   $214.20  
  7 purchase totals = $1,179.74       $1,282.7754   $1,282.78   $1,282.85   $1,282.80