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	$99.45	12.565%	$111.9459	$111.95	$111.95	$111.90
Purchase #2	$141.56	3.753%	$146.8727	$146.87	$146.85	$146.90
Purchase #3	$15.81	7.489%	$16.994	$16.99	$17.00	$17.00
Purchase #4	$223.32	11.497%	$248.9951	$249.00	$249.00	$249.00
Purchase #5	$99.84	10.121%	$109.9448	$109.94	$109.95	$109.90
Purchase #6	$152.28	10.367%	$168.0669	$168.07	$168.05	$168.10
Purchase #7	$241.44	3.470%	$249.818	$249.82	$249.80	$249.80
7 purchase totals =	$973.70		$1,052.6374	$1,052.64	$1,052.60	$1,052.60