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 $170.62   13.672%   $193.9472   $193.95   $193.95   $193.90  
  Purchase #2 $220.25   9.826%   $241.8918   $241.89   $241.90   $241.90  
  Purchase #3 $89.96   4.459%   $93.9713   $93.97   $93.95   $94.00  
  Purchase #4 $231.92   10.323%   $255.8611   $255.86   $255.85   $255.90  
  Purchase #5 $152.52   9.601%   $167.1634   $167.16   $167.15   $167.20  
  Purchase #6 $225.58   3.297%   $233.0174   $233.02   $233.00   $233.00  
  Purchase #7 $167.49   6.726%   $178.7554   $178.76   $178.75   $178.80  
  7 purchase totals = $1,258.34       $1,364.6076   $1,364.61   $1,364.55   $1,364.70