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	$159.95	11.831%	$178.8737	$178.87	$178.85	$178.90
Purchase #2	$121.94	7.485%	$131.0672	$131.07	$131.05	$131.10
Purchase #3	$154.89	13.179%	$175.303	$175.30	$175.30	$175.30
Purchase #4	$156.57	10.452%	$172.9347	$172.93	$172.95	$172.90
Purchase #5	$42.75	7.135%	$45.8002	$45.80	$45.80	$45.80
Purchase #6	$245.52	3.196%	$253.3668	$253.37	$253.35	$253.40
Purchase #7	$164.98	7.561%	$177.4541	$177.45	$177.45	$177.50
7 purchase totals =	$1,046.60		$1,134.7997	$1,134.79	$1,134.75	$1,134.90