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	$98.61	7.235%	$105.7444	$105.74	$105.75	$105.70
Purchase #2	$8.26	10.463%	$9.1242	$9.12	$9.10	$9.10
Purchase #3	$59.25	12.871%	$66.8761	$66.88	$66.90	$66.90
Purchase #4	$49.79	5.479%	$52.518	$52.52	$52.50	$52.50
Purchase #5	$236.74	9.631%	$259.5404	$259.54	$259.55	$259.50
Purchase #6	$146.55	6.804%	$156.5213	$156.52	$156.50	$156.50
Purchase #7	$127.83	11.388%	$142.3873	$142.39	$142.40	$142.40
7 purchase totals =	$727.03		$792.7117	$792.71	$792.70	$792.60