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	$228.43	5.230%	$240.3769	$240.38	$240.40	$240.40
Purchase #2	$43.34	4.522%	$45.2998	$45.30	$45.30	$45.30
Purchase #3	$63.31	12.713%	$71.3586	$71.36	$71.35	$71.40
Purchase #4	$170.90	3.428%	$176.7585	$176.76	$176.75	$176.80
Purchase #5	$65.39	4.704%	$68.4659	$68.47	$68.45	$68.50
Purchase #6	$8.34	9.114%	$9.1001	$9.10	$9.10	$9.10
Purchase #7	$37.60	13.834%	$42.8016	$42.80	$42.80	$42.80
7 purchase totals =	$617.31		$654.1614	$654.17	$654.15	$654.30