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	$128.52	13.118%	$145.3793	$145.38	$145.40	$145.40
Purchase #2	$51.47	7.793%	$55.4811	$55.48	$55.50	$55.50
Purchase #3	$248.35	7.573%	$267.1575	$267.16	$267.15	$267.20
Purchase #4	$176.68	13.665%	$200.8233	$200.82	$200.80	$200.80
Purchase #5	$60.29	7.521%	$64.8244	$64.82	$64.80	$64.80
Purchase #6	$155.47	10.766%	$172.2079	$172.21	$172.20	$172.20
Purchase #7	$28.69	6.589%	$30.5804	$30.58	$30.60	$30.60
7 purchase totals =	$849.47		$936.4539	$936.45	$936.45	$936.50