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	$235.91	7.794%	$254.2968	$254.30	$254.30	$254.30
Purchase #2	$92.31	4.116%	$96.1095	$96.11	$96.10	$96.10
Purchase #3	$99.28	9.787%	$108.9965	$109.00	$109.00	$109.00
Purchase #4	$192.99	13.166%	$218.3991	$218.40	$218.40	$218.40
Purchase #5	$150.43	8.240%	$162.8254	$162.83	$162.85	$162.80
Purchase #6	$142.96	6.823%	$152.7142	$152.71	$152.70	$152.70
Purchase #7	$20.51	13.273%	$23.2323	$23.23	$23.25	$23.20
7 purchase totals =	$934.39		$1,016.5738	$1,016.58	$1,016.60	$1,016.50