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 $176.85   11.598%   $197.3611   $197.36   $197.35   $197.40  
  Purchase #2 $75.60   8.750%   $82.215   $82.22   $82.20   $82.20  
  Purchase #3 $107.61   11.553%   $120.0422   $120.04   $120.05   $120.00  
  Purchase #4 $167.59   3.383%   $173.2596   $173.26   $173.25   $173.30  
  Purchase #5 $195.69   8.696%   $212.7072   $212.71   $212.70   $212.70  
  Purchase #6 $209.57   4.347%   $218.68   $218.68   $218.70   $218.70  
  Purchase #7 $184.49   9.716%   $202.415   $202.42   $202.40   $202.40  
  7 purchase totals = $1,117.40       $1,206.6801   $1,206.69   $1,206.65   $1,206.70