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	$55.28	3.721%	$57.337	$57.34	$57.35	$57.30
Purchase #2	$202.25	5.149%	$212.6639	$212.66	$212.65	$212.70
Purchase #3	$148.29	11.289%	$165.0305	$165.03	$165.05	$165.00
Purchase #4	$74.81	11.419%	$83.3526	$83.35	$83.35	$83.40
Purchase #5	$164.37	13.805%	$187.0613	$187.06	$187.05	$187.10
Purchase #6	$152.45	13.428%	$172.921	$172.92	$172.90	$172.90
Purchase #7	$221.60	4.439%	$231.4368	$231.44	$231.45	$231.40
7 purchase totals =	$1,019.05		$1,109.8031	$1,109.80	$1,109.80	$1,109.80