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	$194.47	11.461%	$216.7582	$216.76	$216.75	$216.80
Purchase #2	$51.47	9.563%	$56.3921	$56.39	$56.40	$56.40
Purchase #3	$173.79	8.501%	$188.5639	$188.56	$188.55	$188.60
Purchase #4	$117.80	12.712%	$132.7747	$132.77	$132.75	$132.80
Purchase #5	$154.55	10.692%	$171.0745	$171.07	$171.05	$171.10
Purchase #6	$204.51	8.694%	$222.2901	$222.29	$222.30	$222.30
Purchase #7	$92.59	8.586%	$100.5398	$100.54	$100.55	$100.50
7 purchase totals =	$989.18		$1,088.3933	$1,088.38	$1,088.35	$1,088.50