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	$126.65	9.149%	$138.2372	$138.24	$138.25	$138.20
Purchase #2	$77.79	8.684%	$84.5453	$84.55	$84.55	$84.50
Purchase #3	$56.30	8.845%	$61.2797	$61.28	$61.30	$61.30
Purchase #4	$143.91	4.516%	$150.409	$150.41	$150.40	$150.40
Purchase #5	$240.62	6.275%	$255.7189	$255.72	$255.70	$255.70
Purchase #6	$98.37	13.534%	$111.6834	$111.68	$111.70	$111.70
Purchase #7	$212.54	4.625%	$222.37	$222.37	$222.35	$222.40
7 purchase totals =	$956.18		$1,024.2435	$1,024.25	$1,024.25	$1,024.20