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	$92.32	5.714%	$97.5952	$97.60	$97.60	$97.60
Purchase #2	$164.35	6.519%	$175.064	$175.06	$175.05	$175.10
Purchase #3	$144.29	10.618%	$159.6107	$159.61	$159.60	$159.60
Purchase #4	$200.63	12.491%	$225.6907	$225.69	$225.70	$225.70
Purchase #5	$79.64	13.236%	$90.1812	$90.18	$90.20	$90.20
Purchase #6	$77.50	9.733%	$85.0431	$85.04	$85.05	$85.00
Purchase #7	$56.83	10.757%	$62.9432	$62.94	$62.95	$62.90
7 purchase totals =	$815.56		$896.1281	$896.12	$896.15	$896.10