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 $85.40   12.851%   $96.3748   $96.37   $96.35   $96.40  
  Purchase #2 $127.41   12.526%   $143.3694   $143.37   $143.35   $143.40  
  Purchase #3 $224.70   8.514%   $243.831   $243.83   $243.85   $243.80  
  Purchase #4 $43.34   5.494%   $45.7211   $45.72   $45.70   $45.70  
  Purchase #5 $152.48   10.130%   $167.9262   $167.93   $167.95   $167.90  
  Purchase #6 $221.51   10.618%   $245.0299   $245.03   $245.05   $245.00  
  Purchase #7 $236.90   6.572%   $252.4691   $252.47   $252.45   $252.50  
  7 purchase totals = $1,091.74       $1,194.7215   $1,194.72   $1,194.70   $1,194.70