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 $90.34   5.139%   $94.9826   $94.98   $95.00   $95.00  
  Purchase #2 $219.50   5.632%   $231.8622   $231.86   $231.85   $231.90  
  Purchase #3 $173.28   7.432%   $186.1582   $186.16   $186.15   $186.20  
  Purchase #4 $241.81   4.746%   $253.2863   $253.29   $253.30   $253.30  
  Purchase #5 $109.57   8.726%   $119.1311   $119.13   $119.15   $119.10  
  Purchase #6 $189.62   12.716%   $213.7321   $213.73   $213.75   $213.70  
  Purchase #7 $35.49   3.713%   $36.8077   $36.81   $36.80   $36.80  
  7 purchase totals = $1,059.61       $1,135.9602   $1,135.96   $1,136.00   $1,136.00