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	$78.84	4.846%	$82.6606	$82.66	$82.65	$82.70
Purchase #2	$66.70	6.859%	$71.275	$71.28	$71.30	$71.30
Purchase #3	$231.83	10.436%	$256.0238	$256.02	$256.00	$256.00
Purchase #4	$148.49	10.139%	$163.5454	$163.55	$163.55	$163.50
Purchase #5	$57.60	5.190%	$60.5894	$60.59	$60.60	$60.60
Purchase #6	$54.31	7.299%	$58.2741	$58.27	$58.25	$58.30
Purchase #7	$106.80	4.603%	$111.716	$111.72	$111.70	$111.70
7 purchase totals =	$744.57		$804.0843	$804.09	$804.05	$804.10