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 $156.96   6.803%   $167.638   $167.64   $167.65   $167.60  
  Purchase #2 $62.61   10.431%   $69.1408   $69.14   $69.15   $69.10  
  Purchase #3 $91.89   5.826%   $97.2435   $97.24   $97.25   $97.20  
  Purchase #4 $242.57   6.608%   $258.599   $258.60   $258.60   $258.60  
  Purchase #5 $215.48   13.714%   $245.0309   $245.03   $245.05   $245.00  
  Purchase #6 $232.62   8.253%   $251.8181   $251.82   $251.80   $251.80  
  Purchase #7 $112.65   8.801%   $122.5643   $122.56   $122.55   $122.60  
  7 purchase totals = $1,114.78       $1,212.0346   $1,212.03   $1,212.05   $1,211.90