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	$144.77	12.487%	$162.8474	$162.85	$162.85	$162.80
Purchase #2	$81.65	9.607%	$89.4941	$89.49	$89.50	$89.50
Purchase #3	$9.76	5.537%	$10.3004	$10.30	$10.30	$10.30
Purchase #4	$27.79	9.307%	$30.3764	$30.38	$30.40	$30.40
Purchase #5	$233.45	3.716%	$242.125	$242.13	$242.15	$242.10
Purchase #6	$237.81	3.277%	$245.603	$245.60	$245.60	$245.60
Purchase #7	$59.34	3.121%	$61.192	$61.19	$61.20	$61.20
7 purchase totals =	$794.57		$841.9383	$841.94	$842.00	$841.90