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 $174.35   11.696%   $194.742   $194.74   $194.75   $194.70  
  Purchase #2 $234.28   13.834%   $266.6903   $266.69   $266.70   $266.70  
  Purchase #3 $116.43   11.784%   $130.1501   $130.15   $130.15   $130.20  
  Purchase #4 $212.54   4.435%   $221.9661   $221.97   $221.95   $222.00  
  Purchase #5 $212.87   5.112%   $223.7519   $223.75   $223.75   $223.80  
  Purchase #6 $250.75   10.418%   $276.8731   $276.87   $276.85   $276.90  
  Purchase #7 $138.70   6.575%   $147.8195   $147.82   $147.80   $147.80  
  7 purchase totals = $1,339.92       $1,461.9930   $1,461.99   $1,461.95   $1,462.10