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 $83.97   12.255%   $94.2605   $94.26   $94.25   $94.30  
  Purchase #2 $152.71   4.138%   $159.0291   $159.03   $159.05   $159.00  
  Purchase #3 $35.68   4.452%   $37.2685   $37.27   $37.25   $37.30  
  Purchase #4 $177.34   6.580%   $189.009   $189.01   $189.00   $189.00  
  Purchase #5 $155.64   12.353%   $174.8662   $174.87   $174.85   $174.90  
  Purchase #6 $178.79   10.332%   $197.2626   $197.26   $197.25   $197.30  
  Purchase #7 $233.83   9.748%   $256.6237   $256.62   $256.60   $256.60  
  7 purchase totals = $1,017.96       $1,108.3196   $1,108.32   $1,108.25   $1,108.40