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	$194.85	9.389%	$213.1445	$213.14	$213.15	$213.10
Purchase #2	$53.59	13.682%	$60.9222	$60.92	$60.90	$60.90
Purchase #3	$52.88	5.784%	$55.9386	$55.94	$55.95	$55.90
Purchase #4	$118.83	7.384%	$127.6044	$127.60	$127.60	$127.60
Purchase #5	$154.48	10.461%	$170.6402	$170.64	$170.65	$170.60
Purchase #6	$193.42	10.225%	$213.1972	$213.20	$213.20	$213.20
Purchase #7	$91.26	9.316%	$99.7618	$99.76	$99.75	$99.80
7 purchase totals =	$859.31		$941.2089	$941.20	$941.20	$941.10