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	$43.41	6.285%	$46.1383	$46.14	$46.15	$46.10
Purchase #2	$132.97	8.794%	$144.6634	$144.66	$144.65	$144.70
Purchase #3	$30.45	10.358%	$33.604	$33.60	$33.60	$33.60
Purchase #4	$53.41	9.647%	$58.5625	$58.56	$58.55	$58.60
Purchase #5	$76.78	11.109%	$85.3095	$85.31	$85.30	$85.30
Purchase #6	$79.71	12.613%	$89.7638	$89.76	$89.75	$89.80
Purchase #7	$30.77	13.429%	$34.9021	$34.90	$34.90	$34.90
7 purchase totals =	$447.50		$492.9436	$492.93	$492.90	$493.00