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	$153.30	13.705%	$174.3098	$174.31	$174.30	$174.30
Purchase #2	$54.66	4.241%	$56.9781	$56.98	$57.00	$57.00
Purchase #3	$138.72	12.185%	$155.623	$155.62	$155.60	$155.60
Purchase #4	$15.89	3.229%	$16.4031	$16.40	$16.40	$16.40
Purchase #5	$54.31	6.727%	$57.9634	$57.96	$57.95	$58.00
Purchase #6	$52.82	6.502%	$56.2544	$56.25	$56.25	$56.30
Purchase #7	$240.31	11.774%	$268.6041	$268.60	$268.60	$268.60
7 purchase totals =	$710.01		$786.1359	$786.12	$786.10	$786.20