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 $181.97   8.781%   $197.9488   $197.95   $197.95   $197.90  
  Purchase #2 $234.94   4.495%   $245.5006   $245.50   $245.50   $245.50  
  Purchase #3 $86.38   11.686%   $96.4744   $96.47   $96.45   $96.50  
  Purchase #4 $167.77   3.673%   $173.9322   $173.93   $173.95   $173.90  
  Purchase #5 $205.74   10.300%   $226.9312   $226.93   $226.95   $226.90  
  Purchase #6 $58.29   5.870%   $61.7116   $61.71   $61.70   $61.70  
  Purchase #7 $64.33   4.667%   $67.3323   $67.33   $67.35   $67.30  
  7 purchase totals = $999.42       $1,069.8311   $1,069.82   $1,069.85   $1,069.70