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	$50.41	6.622%	$53.7482	$53.75	$53.75	$53.70
Purchase #2	$134.26	10.445%	$148.2835	$148.28	$148.30	$148.30
Purchase #3	$33.94	6.314%	$36.083	$36.08	$36.10	$36.10
Purchase #4	$233.93	13.329%	$265.1105	$265.11	$265.10	$265.10
Purchase #5	$152.33	4.138%	$158.6334	$158.63	$158.65	$158.60
Purchase #6	$230.25	10.170%	$253.6664	$253.67	$253.65	$253.70
Purchase #7	$226.42	12.861%	$255.5399	$255.54	$255.55	$255.50
7 purchase totals =	$1,061.54		$1,171.0649	$1,171.06	$1,171.10	$1,171.00