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	$53.79	8.838%	$58.544	$58.54	$58.55	$58.50
Purchase #2	$186.73	12.242%	$209.5895	$209.59	$209.60	$209.60
Purchase #3	$208.81	6.390%	$222.153	$222.15	$222.15	$222.20
Purchase #4	$160.93	3.189%	$166.0621	$166.06	$166.05	$166.10
Purchase #5	$212.93	8.229%	$230.452	$230.45	$230.45	$230.50
Purchase #6	$26.33	9.846%	$28.9225	$28.92	$28.90	$28.90
Purchase #7	$233.27	11.229%	$259.4639	$259.46	$259.45	$259.50
7 purchase totals =	$1,082.79		$1,175.1870	$1,175.17	$1,175.15	$1,175.30