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	$123.46	3.539%	$127.8292	$127.83	$127.85	$127.80
Purchase #2	$142.72	8.220%	$154.4516	$154.45	$154.45	$154.50
Purchase #3	$125.59	5.506%	$132.505	$132.51	$132.50	$132.50
Purchase #4	$45.87	5.589%	$48.4337	$48.43	$48.45	$48.40
Purchase #5	$160.91	3.228%	$166.1042	$166.10	$166.10	$166.10
Purchase #6	$181.52	4.497%	$189.683	$189.68	$189.70	$189.70
Purchase #7	$142.48	7.750%	$153.5222	$153.52	$153.50	$153.50
7 purchase totals =	$922.55		$972.5289	$972.52	$972.55	$972.50