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	$229.75	11.395%	$255.93	$255.93	$255.95	$255.90
Purchase #2	$44.34	10.838%	$49.1456	$49.15	$49.15	$49.10
Purchase #3	$134.91	8.562%	$146.461	$146.46	$146.45	$146.50
Purchase #4	$93.47	5.435%	$98.5501	$98.55	$98.55	$98.60
Purchase #5	$138.32	11.729%	$154.5436	$154.54	$154.55	$154.50
Purchase #6	$211.40	11.234%	$235.1487	$235.15	$235.15	$235.10
Purchase #7	$140.88	12.190%	$158.0533	$158.05	$158.05	$158.10
7 purchase totals =	$993.07		$1,097.8323	$1,097.83	$1,097.85	$1,097.80