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	$204.62	7.801%	$220.5824	$220.58	$220.60	$220.60
Purchase #2	$43.54	7.713%	$46.8982	$46.90	$46.90	$46.90
Purchase #3	$10.85	13.229%	$12.2853	$12.29	$12.30	$12.30
Purchase #4	$221.66	4.188%	$230.9431	$230.94	$230.95	$230.90
Purchase #5	$58.67	9.469%	$64.2255	$64.23	$64.25	$64.20
Purchase #6	$49.55	5.423%	$52.2371	$52.24	$52.25	$52.20
Purchase #7	$143.70	6.387%	$152.8781	$152.88	$152.90	$152.90
7 purchase totals =	$732.59		$780.0497	$780.06	$780.15	$780.00