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	$69.31	6.548%	$73.8484	$73.85	$73.85	$73.80
Purchase #2	$233.94	4.534%	$244.5468	$244.55	$244.55	$244.50
Purchase #3	$215.27	8.435%	$233.428	$233.43	$233.45	$233.40
Purchase #4	$78.43	10.849%	$86.9389	$86.94	$86.95	$86.90
Purchase #5	$57.35	8.607%	$62.2861	$62.29	$62.30	$62.30
Purchase #6	$200.28	7.284%	$214.8684	$214.87	$214.85	$214.90
Purchase #7	$159.99	3.337%	$165.3289	$165.33	$165.35	$165.30
7 purchase totals =	$1,014.57		$1,081.2455	$1,081.26	$1,081.30	$1,081.10