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 $172.47   13.298%   $195.4051   $195.41   $195.40   $195.40  
  Purchase #2 $88.71   7.292%   $95.1787   $95.18   $95.20   $95.20  
  Purchase #3 $181.36   11.253%   $201.7684   $201.77   $201.75   $201.80  
  Purchase #4 $56.58   7.690%   $60.931   $60.93   $60.95   $60.90  
  Purchase #5 $232.89   4.839%   $244.1595   $244.16   $244.15   $244.20  
  Purchase #6 $224.77   10.762%   $248.9597   $248.96   $248.95   $249.00  
  Purchase #7 $150.41   11.237%   $167.3116   $167.31   $167.30   $167.30  
  7 purchase totals = $1,107.19       $1,213.7140   $1,213.72   $1,213.70   $1,213.80