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	$178.31	11.858%	$199.454	$199.45	$199.45	$199.50
Purchase #2	$129.99	6.287%	$138.1625	$138.16	$138.15	$138.20
Purchase #3	$72.66	12.344%	$81.6292	$81.63	$81.65	$81.60
Purchase #4	$95.31	4.797%	$99.882	$99.88	$99.90	$99.90
Purchase #5	$187.66	3.240%	$193.7402	$193.74	$193.75	$193.70
Purchase #6	$214.40	7.176%	$229.7853	$229.79	$229.80	$229.80
Purchase #7	$238.27	6.547%	$253.8695	$253.87	$253.85	$253.90
7 purchase totals =	$1,116.60		$1,196.5227	$1,196.52	$1,196.55	$1,196.60