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 $68.50   7.674%   $73.7567   $73.76   $73.75   $73.80  
  Purchase #2 $179.76   9.319%   $196.5118   $196.51   $196.50   $196.50  
  Purchase #3 $164.55   10.549%   $181.9084   $181.91   $181.90   $181.90  
  Purchase #4 $114.95   6.327%   $122.2229   $122.22   $122.20   $122.20  
  Purchase #5 $201.94   10.598%   $223.3416   $223.34   $223.35   $223.30  
  Purchase #6 $192.47   11.664%   $214.9197   $214.92   $214.90   $214.90  
  Purchase #7 $197.70   3.585%   $204.7875   $204.79   $204.80   $204.80  
  7 purchase totals = $1,119.87       $1,217.4486   $1,217.45   $1,217.40   $1,217.40