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	$132.61	7.317%	$142.3131	$142.31	$142.30	$142.30
Purchase #2	$218.82	5.192%	$230.1811	$230.18	$230.20	$230.20
Purchase #3	$66.78	6.239%	$70.9464	$70.95	$70.95	$70.90
Purchase #4	$69.77	12.506%	$78.4954	$78.50	$78.50	$78.50
Purchase #5	$71.51	8.343%	$77.4761	$77.48	$77.50	$77.50
Purchase #6	$60.28	6.730%	$64.3368	$64.34	$64.35	$64.30
Purchase #7	$105.55	5.470%	$111.3236	$111.32	$111.30	$111.30
7 purchase totals =	$725.32		$775.0725	$775.08	$775.10	$775.00