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	$142.74	5.418%	$150.4737	$150.47	$150.45	$150.50
Purchase #2	$8.50	3.362%	$8.7858	$8.79	$8.80	$8.80
Purchase #3	$223.79	6.645%	$238.6608	$238.66	$238.65	$238.70
Purchase #4	$179.39	4.282%	$187.0715	$187.07	$187.05	$187.10
Purchase #5	$99.46	12.122%	$111.5165	$111.52	$111.50	$111.50
Purchase #6	$208.72	8.643%	$226.7597	$226.76	$226.75	$226.80
Purchase #7	$231.80	10.825%	$256.8924	$256.89	$256.90	$256.90
7 purchase totals =	$1,094.40		$1,180.1604	$1,180.16	$1,180.10	$1,180.30