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 $226.28   3.851%   $234.994   $234.99   $235.00   $235.00  
  Purchase #2 $199.27   9.385%   $217.9715   $217.97   $217.95   $218.00  
  Purchase #3 $192.94   5.684%   $203.9067   $203.91   $203.90   $203.90  
  Purchase #4 $197.60   7.709%   $212.833   $212.83   $212.85   $212.80  
  Purchase #5 $203.42   11.215%   $226.2336   $226.23   $226.25   $226.20  
  Purchase #6 $90.71   4.707%   $94.9797   $94.98   $95.00   $95.00  
  Purchase #7 $18.62   11.513%   $20.7637   $20.76   $20.75   $20.80  
  7 purchase totals = $1,128.84       $1,211.6822   $1,211.67   $1,211.70   $1,211.70