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	$124.82	7.304%	$133.9369	$133.94	$133.95	$133.90
Purchase #2	$100.65	10.472%	$111.1901	$111.19	$111.20	$111.20
Purchase #3	$11.97	11.247%	$13.3163	$13.32	$13.30	$13.30
Purchase #4	$79.74	9.780%	$87.5386	$87.54	$87.55	$87.50
Purchase #5	$238.28	6.698%	$254.24	$254.24	$254.25	$254.20
Purchase #6	$158.90	6.688%	$169.5272	$169.53	$169.55	$169.50
Purchase #7	$17.46	7.182%	$18.714	$18.71	$18.70	$18.70
7 purchase totals =	$731.82		$788.4631	$788.47	$788.50	$788.30