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	$202.54	8.548%	$219.8531	$219.85	$219.85	$219.90
Purchase #2	$196.55	4.243%	$204.8896	$204.89	$204.90	$204.90
Purchase #3	$153.56	9.235%	$167.7413	$167.74	$167.75	$167.70
Purchase #4	$52.38	5.623%	$55.3253	$55.33	$55.35	$55.30
Purchase #5	$114.55	10.260%	$126.3028	$126.30	$126.30	$126.30
Purchase #6	$71.90	13.244%	$81.4224	$81.42	$81.40	$81.40
Purchase #7	$42.55	7.414%	$45.7047	$45.70	$45.70	$45.70
7 purchase totals =	$834.03		$901.2392	$901.23	$901.25	$901.20