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 $175.65   11.407%   $195.6864   $195.69   $195.70   $195.70  
  Purchase #2 $242.73   8.452%   $263.2455   $263.25   $263.25   $263.20  
  Purchase #3 $61.25   4.802%   $64.1912   $64.19   $64.20   $64.20  
  Purchase #4 $128.60   12.401%   $144.5477   $144.55   $144.55   $144.50  
  Purchase #5 $86.85   9.170%   $94.8141   $94.81   $94.80   $94.80  
  Purchase #6 $152.89   3.322%   $157.969   $157.97   $157.95   $158.00  
  Purchase #7 $220.33   9.441%   $241.1314   $241.13   $241.15   $241.10  
  7 purchase totals = $1,068.30       $1,161.5853   $1,161.59   $1,161.60   $1,161.50