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	$226.82	11.820%	$253.6301	$253.63	$253.65	$253.60
Purchase #2	$211.35	7.736%	$227.7	$227.70	$227.70	$227.70
Purchase #3	$158.35	13.343%	$179.4786	$179.48	$179.50	$179.50
Purchase #4	$230.77	7.422%	$247.8977	$247.90	$247.90	$247.90
Purchase #5	$32.56	5.200%	$34.2531	$34.25	$34.25	$34.30
Purchase #6	$208.80	9.375%	$228.375	$228.38	$228.40	$228.40
Purchase #7	$89.76	11.142%	$99.7611	$99.76	$99.75	$99.80
7 purchase totals =	$1,158.41		$1,271.0956	$1,271.10	$1,271.15	$1,271.20