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	$78.61	13.303%	$89.0675	$89.07	$89.05	$89.10
Purchase #2	$106.33	10.615%	$117.6169	$117.62	$117.60	$117.60
Purchase #3	$45.91	6.261%	$48.7844	$48.78	$48.80	$48.80
Purchase #4	$154.52	11.714%	$172.6205	$172.62	$172.60	$172.60
Purchase #5	$227.41	3.457%	$235.2716	$235.27	$235.25	$235.30
Purchase #6	$68.97	12.548%	$77.6244	$77.62	$77.60	$77.60
Purchase #7	$167.31	10.144%	$184.2819	$184.28	$184.30	$184.30
7 purchase totals =	$849.06		$925.2672	$925.26	$925.20	$925.30