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	$64.71	10.697%	$71.632	$71.63	$71.65	$71.60
Purchase #2	$131.60	10.145%	$144.9508	$144.95	$144.95	$145.00
Purchase #3	$72.99	11.563%	$81.4298	$81.43	$81.45	$81.40
Purchase #4	$152.29	6.162%	$161.6741	$161.67	$161.65	$161.70
Purchase #5	$140.62	3.364%	$145.3505	$145.35	$145.35	$145.40
Purchase #6	$83.45	7.852%	$90.0025	$90.00	$90.00	$90.00
Purchase #7	$181.63	4.782%	$190.3155	$190.32	$190.30	$190.30
7 purchase totals =	$827.29		$885.3552	$885.35	$885.35	$885.40