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	$40.89	13.469%	$46.3975	$46.40	$46.40	$46.40
Purchase #2	$44.78	7.205%	$48.0064	$48.01	$48.00	$48.00
Purchase #3	$118.51	7.218%	$127.0641	$127.06	$127.05	$127.10
Purchase #4	$141.35	4.420%	$147.5977	$147.60	$147.60	$147.60
Purchase #5	$116.59	9.233%	$127.3548	$127.35	$127.35	$127.40
Purchase #6	$82.31	11.437%	$91.7238	$91.72	$91.70	$91.70
Purchase #7	$165.84	8.861%	$180.5351	$180.54	$180.55	$180.50
7 purchase totals =	$710.27		$768.6794	$768.68	$768.65	$768.70