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	7.829%	$59.6079	$59.61	$59.60	$59.60
Purchase #2	$103.52	7.472%	$111.255	$111.26	$111.25	$111.30
Purchase #3	$113.69	4.345%	$118.6298	$118.63	$118.65	$118.60
Purchase #4	$142.77	8.442%	$154.8226	$154.82	$154.80	$154.80
Purchase #5	$239.71	7.308%	$257.228	$257.23	$257.25	$257.20
Purchase #6	$21.79	3.786%	$22.615	$22.62	$22.60	$22.60
Purchase #7	$168.25	7.766%	$181.3163	$181.32	$181.30	$181.30
7 purchase totals =	$845.01		$905.4746	$905.49	$905.45	$905.40