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	$189.98	3.503%	$196.635	$196.64	$196.65	$196.60
Purchase #2	$229.50	10.388%	$253.3405	$253.34	$253.35	$253.30
Purchase #3	$234.35	11.434%	$261.1456	$261.15	$261.15	$261.10
Purchase #4	$28.29	4.471%	$29.5548	$29.55	$29.55	$29.60
Purchase #5	$166.88	7.574%	$179.5195	$179.52	$179.50	$179.50
Purchase #6	$129.42	10.278%	$142.7218	$142.72	$142.70	$142.70
Purchase #7	$188.30	3.386%	$194.6758	$194.68	$194.70	$194.70
7 purchase totals =	$1,166.72		$1,257.5930	$1,257.60	$1,257.60	$1,257.50