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	$159.52	8.165%	$172.5448	$172.54	$172.55	$172.50
Purchase #2	$148.25	5.727%	$156.7403	$156.74	$156.75	$156.70
Purchase #3	$202.45	6.602%	$215.8157	$215.82	$215.80	$215.80
Purchase #4	$111.92	13.849%	$127.4198	$127.42	$127.40	$127.40
Purchase #5	$170.42	3.649%	$176.6386	$176.64	$176.65	$176.60
Purchase #6	$144.85	11.482%	$161.4817	$161.48	$161.50	$161.50
Purchase #7	$17.91	13.480%	$20.3243	$20.32	$20.30	$20.30
7 purchase totals =	$955.32		$1,030.9652	$1,030.96	$1,030.95	$1,030.80