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 $67.41   6.347%   $71.6885   $71.69   $71.70   $71.70  
  Purchase #2 $167.54   9.440%   $183.3558   $183.36   $183.35   $183.40  
  Purchase #3 $118.58   3.525%   $122.7599   $122.76   $122.75   $122.80  
  Purchase #4 $146.39   13.472%   $166.1117   $166.11   $166.10   $166.10  
  Purchase #5 $222.61   9.715%   $244.2366   $244.24   $244.25   $244.20  
  Purchase #6 $171.59   4.299%   $178.9667   $178.97   $178.95   $179.00  
  Purchase #7 $219.30   12.266%   $246.1993   $246.20   $246.20   $246.20  
  7 purchase totals = $1,113.42       $1,213.3185   $1,213.33   $1,213.30   $1,213.40