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	$72.75	10.862%	$80.6521	$80.65	$80.65	$80.70
Purchase #2	$233.26	9.755%	$256.0145	$256.01	$256.00	$256.00
Purchase #3	$16.39	10.504%	$18.1116	$18.11	$18.10	$18.10
Purchase #4	$226.95	10.259%	$250.2328	$250.23	$250.25	$250.20
Purchase #5	$42.84	3.692%	$44.4217	$44.42	$44.40	$44.40
Purchase #6	$242.38	12.189%	$271.9237	$271.92	$271.90	$271.90
Purchase #7	$229.46	11.354%	$255.5129	$255.51	$255.50	$255.50
7 purchase totals =	$1,064.03		$1,176.8693	$1,176.85	$1,176.80	$1,176.80