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	$155.89	13.496%	$176.9289	$176.93	$176.95	$176.90
Purchase #2	$216.56	5.374%	$228.1979	$228.20	$228.20	$228.20
Purchase #3	$52.44	7.330%	$56.2839	$56.28	$56.30	$56.30
Purchase #4	$47.44	9.865%	$52.12	$52.12	$52.10	$52.10
Purchase #5	$73.75	6.599%	$78.6168	$78.62	$78.60	$78.60
Purchase #6	$241.60	13.601%	$274.46	$274.46	$274.45	$274.50
Purchase #7	$156.77	10.495%	$173.223	$173.22	$173.20	$173.20
7 purchase totals =	$944.45		$1,039.8305	$1,039.83	$1,039.80	$1,039.80