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 $84.61   12.275%   $94.9959   $95.00   $95.00   $95.00  
  Purchase #2 $22.77   5.384%   $23.9959   $24.00   $24.00   $24.00  
  Purchase #3 $92.91   6.535%   $98.9817   $98.98   $99.00   $99.00  
  Purchase #4 $101.70   7.705%   $109.536   $109.54   $109.55   $109.50  
  Purchase #5 $160.39   5.327%   $168.934   $168.93   $168.95   $168.90  
  Purchase #6 $153.30   4.518%   $160.2261   $160.23   $160.25   $160.20  
  Purchase #7 $51.80   8.251%   $56.074   $56.07   $56.05   $56.10  
  7 purchase totals = $667.48       $712.7436   $712.75   $712.80   $712.70