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	$60.84	7.733%	$65.5448	$65.54	$65.55	$65.50
Purchase #2	$79.40	7.362%	$85.2454	$85.25	$85.25	$85.20
Purchase #3	$94.88	4.522%	$99.1705	$99.17	$99.15	$99.20
Purchase #4	$170.85	4.294%	$178.1863	$178.19	$178.20	$178.20
Purchase #5	$83.62	4.344%	$87.2525	$87.25	$87.25	$87.30
Purchase #6	$207.59	7.481%	$223.1198	$223.12	$223.10	$223.10
Purchase #7	$179.59	5.832%	$190.0637	$190.06	$190.05	$190.10
7 purchase totals =	$876.77		$928.5830	$928.58	$928.55	$928.60