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 $38.33   13.343%   $43.4444   $43.44   $43.45   $43.40  
  Purchase #2 $95.86   11.565%   $106.9462   $106.95   $106.95   $106.90  
  Purchase #3 $90.37   6.480%   $96.226   $96.23   $96.25   $96.20  
  Purchase #4 $83.34   9.510%   $91.2656   $91.27   $91.25   $91.30  
  Purchase #5 $97.62   4.222%   $101.7415   $101.74   $101.75   $101.70  
  Purchase #6 $195.58   7.494%   $210.2368   $210.24   $210.25   $210.20  
  Purchase #7 $204.66   3.527%   $211.8784   $211.88   $211.90   $211.90  
  7 purchase totals = $805.76       $861.7389   $861.75   $861.80   $861.60