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	$92.35	11.599%	$103.0617	$103.06	$103.05	$103.10
Purchase #2	$228.65	12.349%	$256.886	$256.89	$256.90	$256.90
Purchase #3	$118.62	9.696%	$130.1214	$130.12	$130.10	$130.10
Purchase #4	$242.58	7.419%	$260.577	$260.58	$260.60	$260.60
Purchase #5	$56.77	6.407%	$60.4073	$60.41	$60.40	$60.40
Purchase #6	$83.81	9.521%	$91.7896	$91.79	$91.80	$91.80
Purchase #7	$221.83	8.846%	$241.4531	$241.45	$241.45	$241.50
7 purchase totals =	$1,044.61		$1,144.2961	$1,144.30	$1,144.30	$1,144.40