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	$214.95	10.436%	$237.3822	$237.38	$237.40	$237.40
Purchase #2	$198.90	6.146%	$211.1244	$211.12	$211.10	$211.10
Purchase #3	$12.49	7.461%	$13.4219	$13.42	$13.40	$13.40
Purchase #4	$177.51	10.492%	$196.1343	$196.13	$196.15	$196.10
Purchase #5	$89.82	13.114%	$101.599	$101.60	$101.60	$101.60
Purchase #6	$91.75	7.267%	$98.4175	$98.42	$98.40	$98.40
Purchase #7	$100.89	11.143%	$112.1322	$112.13	$112.15	$112.10
7 purchase totals =	$886.31		$970.2115	$970.20	$970.20	$970.10