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 $61.93   5.419%   $65.286   $65.29   $65.30   $65.30  
  Purchase #2 $111.70   12.148%   $125.2693   $125.27   $125.25   $125.30  
  Purchase #3 $125.27   4.708%   $131.1677   $131.17   $131.15   $131.20  
  Purchase #4 $26.35   10.407%   $29.0922   $29.09   $29.10   $29.10  
  Purchase #5 $186.40   7.136%   $199.7015   $199.70   $199.70   $199.70  
  Purchase #6 $214.94   10.299%   $237.0767   $237.08   $237.10   $237.10  
  Purchase #7 $159.46   3.489%   $165.0236   $165.02   $165.00   $165.00  
  7 purchase totals = $886.05       $952.6170   $952.62   $952.60   $952.70