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	$73.37	6.855%	$78.3995	$78.40	$78.40	$78.40
Purchase #2	$29.95	12.774%	$33.7758	$33.78	$33.80	$33.80
Purchase #3	$162.82	6.405%	$173.2486	$173.25	$173.25	$173.20
Purchase #4	$163.79	8.727%	$178.084	$178.08	$178.10	$178.10
Purchase #5	$187.83	6.578%	$200.1855	$200.19	$200.20	$200.20
Purchase #6	$74.51	5.118%	$78.3234	$78.32	$78.30	$78.30
Purchase #7	$71.52	4.406%	$74.6712	$74.67	$74.65	$74.70
7 purchase totals =	$763.79		$816.6880	$816.69	$816.70	$816.70