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	$94.56	6.362%	$100.5759	$100.58	$100.60	$100.60
Purchase #2	$21.66	4.381%	$22.6089	$22.61	$22.60	$22.60
Purchase #3	$248.68	5.162%	$261.5169	$261.52	$261.50	$261.50
Purchase #4	$209.61	12.115%	$235.0043	$235.00	$235.00	$235.00
Purchase #5	$155.25	8.428%	$168.3345	$168.33	$168.35	$168.30
Purchase #6	$206.52	13.256%	$233.8963	$233.90	$233.90	$233.90
Purchase #7	$39.58	13.836%	$45.0563	$45.06	$45.05	$45.10
7 purchase totals =	$975.86		$1,066.9931	$1,067.00	$1,067.00	$1,067.00