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 $182.85   5.493%   $192.894   $192.89   $192.90   $192.90  
  Purchase #2 $174.39   12.227%   $195.7127   $195.71   $195.70   $195.70  
  Purchase #3 $154.67   6.747%   $165.1056   $165.11   $165.10   $165.10  
  Purchase #4 $71.87   11.499%   $80.1343   $80.13   $80.15   $80.10  
  Purchase #5 $83.86   12.738%   $94.5421   $94.54   $94.55   $94.50  
  Purchase #6 $122.69   13.206%   $138.8924   $138.89   $138.90   $138.90  
  Purchase #7 $136.45   8.454%   $147.9855   $147.99   $148.00   $148.00  
  7 purchase totals = $926.78       $1,015.2666   $1,015.26   $1,015.30   $1,015.20