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	$211.48	13.600%	$240.2413	$240.24	$240.25	$240.20
Purchase #2	$101.74	6.662%	$108.5179	$108.52	$108.50	$108.50
Purchase #3	$110.72	5.212%	$116.4907	$116.49	$116.50	$116.50
Purchase #4	$220.68	12.615%	$248.5188	$248.52	$248.50	$248.50
Purchase #5	$212.60	13.244%	$240.7567	$240.76	$240.75	$240.80
Purchase #6	$80.68	10.820%	$89.4096	$89.41	$89.40	$89.40
Purchase #7	$100.45	10.832%	$111.3307	$111.33	$111.35	$111.30
7 purchase totals =	$1,038.35		$1,155.2657	$1,155.27	$1,155.25	$1,155.20