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	$52.62	12.708%	$59.3069	$59.31	$59.30	$59.30
Purchase #2	$195.42	10.745%	$216.4179	$216.42	$216.40	$216.40
Purchase #3	$186.60	6.366%	$198.479	$198.48	$198.50	$198.50
Purchase #4	$128.77	3.841%	$133.7161	$133.72	$133.70	$133.70
Purchase #5	$214.28	13.429%	$243.0557	$243.06	$243.05	$243.10
Purchase #6	$127.79	5.112%	$134.3226	$134.32	$134.30	$134.30
Purchase #7	$167.27	3.552%	$173.2114	$173.21	$173.20	$173.20
7 purchase totals =	$1,072.75		$1,158.5096	$1,158.52	$1,158.45	$1,158.50