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	$238.59	3.580%	$247.1315	$247.13	$247.15	$247.10
Purchase #2	$75.28	5.525%	$79.4392	$79.44	$79.45	$79.40
Purchase #3	$147.46	6.173%	$156.5627	$156.56	$156.55	$156.60
Purchase #4	$132.85	9.269%	$145.1639	$145.16	$145.15	$145.20
Purchase #5	$126.91	3.463%	$131.3049	$131.30	$131.30	$131.30
Purchase #6	$80.43	12.649%	$90.6036	$90.60	$90.60	$90.60
Purchase #7	$137.27	12.154%	$153.9538	$153.95	$153.95	$154.00
7 purchase totals =	$938.79		$1,004.1596	$1,004.14	$1,004.15	$1,004.20