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	$227.50	5.858%	$240.827	$240.83	$240.85	$240.80
Purchase #2	$20.45	7.661%	$22.0167	$22.02	$22.00	$22.00
Purchase #3	$100.80	10.247%	$111.129	$111.13	$111.15	$111.10
Purchase #4	$221.52	12.384%	$248.953	$248.95	$248.95	$249.00
Purchase #5	$106.94	6.263%	$113.6377	$113.64	$113.65	$113.60
Purchase #6	$216.56	10.539%	$239.3833	$239.38	$239.40	$239.40
Purchase #7	$142.55	6.306%	$151.5392	$151.54	$151.55	$151.50
7 purchase totals =	$1,036.32		$1,127.4859	$1,127.49	$1,127.55	$1,127.40