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	$57.83	9.829%	$63.5141	$63.51	$63.50	$63.50
Purchase #2	$127.88	7.747%	$137.7869	$137.79	$137.80	$137.80
Purchase #3	$169.79	9.118%	$185.2715	$185.27	$185.25	$185.30
Purchase #4	$207.51	11.834%	$232.0667	$232.07	$232.05	$232.10
Purchase #5	$155.95	6.193%	$165.608	$165.61	$165.60	$165.60
Purchase #6	$233.54	5.363%	$246.0648	$246.06	$246.05	$246.10
Purchase #7	$50.63	6.786%	$54.0658	$54.07	$54.05	$54.10
7 purchase totals =	$1,003.13		$1,084.3778	$1,084.38	$1,084.30	$1,084.50