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	$168.96	7.335%	$181.3532	$181.35	$181.35	$181.40
Purchase #2	$145.58	5.155%	$153.0846	$153.08	$153.10	$153.10
Purchase #3	$50.30	6.415%	$53.5267	$53.53	$53.55	$53.50
Purchase #4	$183.31	3.691%	$190.076	$190.08	$190.10	$190.10
Purchase #5	$38.85	10.353%	$42.8721	$42.87	$42.85	$42.90
Purchase #6	$191.57	9.426%	$209.6274	$209.63	$209.65	$209.60
Purchase #7	$116.33	9.348%	$127.2045	$127.20	$127.20	$127.20
7 purchase totals =	$894.90		$957.7445	$957.74	$957.80	$957.80