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	$98.87	13.858%	$112.5714	$112.57	$112.55	$112.60
Purchase #2	$99.35	6.200%	$105.5097	$105.51	$105.50	$105.50
Purchase #3	$37.77	10.686%	$41.8061	$41.81	$41.80	$41.80
Purchase #4	$192.78	3.797%	$200.0999	$200.10	$200.10	$200.10
Purchase #5	$14.55	7.751%	$15.6778	$15.68	$15.70	$15.70
Purchase #6	$80.50	6.715%	$85.9056	$85.91	$85.90	$85.90
Purchase #7	$136.33	13.465%	$154.6868	$154.69	$154.70	$154.70
7 purchase totals =	$660.15		$716.2573	$716.27	$716.25	$716.30