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	$48.40	11.687%	$54.0565	$54.06	$54.05	$54.10
Purchase #2	$10.98	7.167%	$11.7669	$11.77	$11.75	$11.80
Purchase #3	$59.36	3.321%	$61.3313	$61.33	$61.35	$61.30
Purchase #4	$49.68	8.324%	$53.8154	$53.82	$53.80	$53.80
Purchase #5	$26.83	5.499%	$28.3054	$28.31	$28.30	$28.30
Purchase #6	$17.89	13.768%	$20.3531	$20.35	$20.35	$20.40
Purchase #7	$185.45	10.105%	$204.1897	$204.19	$204.20	$204.20
7 purchase totals =	$398.59		$433.8183	$433.83	$433.80	$433.90