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 $168.28   9.523%   $184.3053   $184.31   $184.30   $184.30  
  Purchase #2 $134.96   11.108%   $149.9514   $149.95   $149.95   $150.00  
  Purchase #3 $201.44   6.213%   $213.9555   $213.96   $213.95   $214.00  
  Purchase #4 $7.99   5.255%   $8.4099   $8.41   $8.40   $8.40  
  Purchase #5 $114.29   6.480%   $121.696   $121.70   $121.70   $121.70  
  Purchase #6 $248.39   9.193%   $271.2245   $271.22   $271.20   $271.20  
  Purchase #7 $247.42   11.422%   $275.6803   $275.68   $275.70   $275.70  
  7 purchase totals = $1,122.77       $1,225.2229   $1,225.23   $1,225.20   $1,225.30