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	$51.31	3.615%	$53.1649	$53.16	$53.15	$53.20
Purchase #2	$158.41	3.600%	$164.1128	$164.11	$164.10	$164.10
Purchase #3	$11.73	7.790%	$12.6438	$12.64	$12.65	$12.60
Purchase #4	$44.52	8.415%	$48.2664	$48.27	$48.25	$48.30
Purchase #5	$6.70	6.218%	$7.1166	$7.12	$7.10	$7.10
Purchase #6	$60.36	3.570%	$62.5149	$62.51	$62.50	$62.50
Purchase #7	$231.45	12.172%	$259.6221	$259.62	$259.60	$259.60
7 purchase totals =	$564.48		$607.4415	$607.43	$607.35	$607.40