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	$227.32	6.206%	$241.4275	$241.43	$241.45	$241.40
Purchase #2	$149.68	3.151%	$154.3964	$154.40	$154.40	$154.40
Purchase #3	$52.67	4.276%	$54.9222	$54.92	$54.90	$54.90
Purchase #4	$6.64	10.848%	$7.3603	$7.36	$7.35	$7.40
Purchase #5	$31.96	4.144%	$33.2844	$33.28	$33.30	$33.30
Purchase #6	$54.65	5.428%	$57.6164	$57.62	$57.60	$57.60
Purchase #7	$74.35	5.181%	$78.2021	$78.20	$78.20	$78.20
7 purchase totals =	$597.27		$627.2093	$627.21	$627.20	$627.20