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	$25.35	11.239%	$28.1991	$28.20	$28.20	$28.20
Purchase #2	$89.61	12.294%	$100.6267	$100.63	$100.65	$100.60
Purchase #3	$156.60	5.450%	$165.1347	$165.13	$165.15	$165.10
Purchase #4	$216.91	11.383%	$241.6009	$241.60	$241.60	$241.60
Purchase #5	$44.96	7.456%	$48.3122	$48.31	$48.30	$48.30
Purchase #6	$47.68	9.327%	$52.1271	$52.13	$52.15	$52.10
Purchase #7	$103.77	8.163%	$112.2407	$112.24	$112.25	$112.20
7 purchase totals =	$684.88		$748.2414	$748.24	$748.30	$748.10