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	$240.64	13.385%	$272.8497	$272.85	$272.85	$272.80
Purchase #2	$171.46	7.218%	$183.836	$183.84	$183.85	$183.80
Purchase #3	$78.66	6.568%	$83.8264	$83.83	$83.85	$83.80
Purchase #4	$209.81	7.434%	$225.4073	$225.41	$225.40	$225.40
Purchase #5	$11.27	11.700%	$12.5886	$12.59	$12.60	$12.60
Purchase #6	$66.62	11.108%	$74.0201	$74.02	$74.00	$74.00
Purchase #7	$159.57	4.371%	$166.5448	$166.54	$166.55	$166.50
7 purchase totals =	$938.03		$1,019.0729	$1,019.08	$1,019.10	$1,018.90