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	$65.73	4.308%	$68.5616	$68.56	$68.55	$68.60
Purchase #2	$85.71	5.163%	$90.1352	$90.14	$90.15	$90.10
Purchase #3	$191.28	12.137%	$214.4957	$214.50	$214.50	$214.50
Purchase #4	$134.66	13.847%	$153.3064	$153.31	$153.30	$153.30
Purchase #5	$116.50	11.208%	$129.5573	$129.56	$129.55	$129.60
Purchase #6	$152.44	4.503%	$159.3044	$159.30	$159.30	$159.30
Purchase #7	$229.77	7.200%	$246.3134	$246.31	$246.30	$246.30
7 purchase totals =	$976.09		$1,061.6740	$1,061.68	$1,061.65	$1,061.70