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	$105.63	5.797%	$111.7534	$111.75	$111.75	$111.80
Purchase #2	$154.65	10.285%	$170.5558	$170.56	$170.55	$170.60
Purchase #3	$144.63	11.227%	$160.8676	$160.87	$160.85	$160.90
Purchase #4	$183.72	13.499%	$208.5204	$208.52	$208.50	$208.50
Purchase #5	$239.46	12.565%	$269.5481	$269.55	$269.55	$269.50
Purchase #6	$249.66	10.497%	$275.8668	$275.87	$275.85	$275.90
Purchase #7	$228.69	7.651%	$246.1871	$246.19	$246.20	$246.20
7 purchase totals =	$1,306.44		$1,443.2992	$1,443.31	$1,443.25	$1,443.40