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	$233.32	4.742%	$244.384	$244.38	$244.40	$244.40
Purchase #2	$127.91	4.479%	$133.6391	$133.64	$133.65	$133.60
Purchase #3	$245.84	13.610%	$279.2988	$279.30	$279.30	$279.30
Purchase #4	$151.89	3.278%	$156.869	$156.87	$156.85	$156.90
Purchase #5	$80.64	8.372%	$87.3912	$87.39	$87.40	$87.40
Purchase #6	$227.77	12.251%	$255.6741	$255.67	$255.65	$255.70
Purchase #7	$51.35	7.536%	$55.2197	$55.22	$55.20	$55.20
7 purchase totals =	$1,118.72		$1,212.4759	$1,212.47	$1,212.45	$1,212.50