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 $214.65   12.561%   $241.6122   $241.61   $241.60   $241.60  
  Purchase #2 $167.97   13.733%   $191.0373   $191.04   $191.05   $191.00  
  Purchase #3 $39.47   13.773%   $44.9062   $44.91   $44.90   $44.90  
  Purchase #4 $161.92   3.164%   $167.0431   $167.04   $167.05   $167.00  
  Purchase #5 $240.98   4.418%   $251.6265   $251.63   $251.65   $251.60  
  Purchase #6 $69.89   4.461%   $73.0078   $73.01   $73.00   $73.00  
  Purchase #7 $220.64   5.874%   $233.6004   $233.60   $233.60   $233.60  
  7 purchase totals = $1,115.52       $1,202.8335   $1,202.84   $1,202.85   $1,202.70