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	$108.29	9.454%	$118.5277	$118.53	$118.55	$118.50
Purchase #2	$209.64	10.236%	$231.0988	$231.10	$231.10	$231.10
Purchase #3	$112.94	4.709%	$118.2583	$118.26	$118.25	$118.30
Purchase #4	$158.52	13.613%	$180.0993	$180.10	$180.10	$180.10
Purchase #5	$49.46	5.261%	$52.0621	$52.06	$52.05	$52.10
Purchase #6	$231.62	9.445%	$253.4965	$253.50	$253.50	$253.50
Purchase #7	$70.80	12.788%	$79.8539	$79.85	$79.85	$79.90
7 purchase totals =	$941.27		$1,033.3966	$1,033.40	$1,033.40	$1,033.50