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	$139.32	10.332%	$153.7145	$153.71	$153.70	$153.70
Purchase #2	$225.93	4.824%	$236.8289	$236.83	$236.85	$236.80
Purchase #3	$55.89	6.399%	$59.4664	$59.47	$59.45	$59.50
Purchase #4	$50.71	7.519%	$54.5229	$54.52	$54.50	$54.50
Purchase #5	$44.35	12.215%	$49.7674	$49.77	$49.75	$49.80
Purchase #6	$242.45	4.869%	$254.2549	$254.25	$254.25	$254.30
Purchase #7	$17.54	5.874%	$18.5703	$18.57	$18.55	$18.60
7 purchase totals =	$776.19		$827.1253	$827.12	$827.05	$827.20