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	$212.68	4.593%	$222.4484	$222.45	$222.45	$222.40
Purchase #2	$222.65	11.331%	$247.8785	$247.88	$247.90	$247.90
Purchase #3	$74.79	4.505%	$78.1593	$78.16	$78.15	$78.20
Purchase #4	$180.73	4.172%	$188.2701	$188.27	$188.25	$188.30
Purchase #5	$167.91	11.450%	$187.1357	$187.14	$187.15	$187.10
Purchase #6	$16.52	6.812%	$17.6453	$17.65	$17.65	$17.60
Purchase #7	$203.32	13.185%	$230.1277	$230.13	$230.15	$230.10
7 purchase totals =	$1,078.60		$1,171.6650	$1,171.68	$1,171.70	$1,171.60