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	$165.84	5.575%	$175.0856	$175.09	$175.10	$175.10
Purchase #2	$148.44	10.532%	$164.0737	$164.07	$164.05	$164.10
Purchase #3	$121.52	4.556%	$127.0565	$127.06	$127.05	$127.10
Purchase #4	$43.78	13.201%	$49.5594	$49.56	$49.55	$49.60
Purchase #5	$126.52	4.658%	$132.4133	$132.41	$132.40	$132.40
Purchase #6	$30.68	3.789%	$31.8425	$31.84	$31.85	$31.80
Purchase #7	$76.72	7.418%	$82.4111	$82.41	$82.40	$82.40
7 purchase totals =	$713.50		$762.4421	$762.44	$762.40	$762.50