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 $94.90   7.407%   $101.9292   $101.93   $101.95   $101.90  
  Purchase #2 $158.97   9.367%   $173.8607   $173.86   $173.85   $173.90  
  Purchase #3 $146.69   5.120%   $154.2005   $154.20   $154.20   $154.20  
  Purchase #4 $206.67   8.709%   $224.6689   $224.67   $224.65   $224.70  
  Purchase #5 $92.61   3.830%   $96.157   $96.16   $96.15   $96.20  
  Purchase #6 $197.84   9.325%   $216.2886   $216.29   $216.30   $216.30  
  Purchase #7 $85.60   12.345%   $96.1673   $96.17   $96.15   $96.20  
  7 purchase totals = $983.28       $1,063.2722   $1,063.28   $1,063.25   $1,063.40