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	$103.51	5.317%	$109.0136	$109.01	$109.00	$109.00
Purchase #2	$235.71	5.265%	$248.1201	$248.12	$248.10	$248.10
Purchase #3	$157.71	9.133%	$172.1137	$172.11	$172.10	$172.10
Purchase #4	$103.25	3.499%	$106.8627	$106.86	$106.85	$106.90
Purchase #5	$77.49	6.590%	$82.5966	$82.60	$82.60	$82.60
Purchase #6	$161.68	6.852%	$172.7583	$172.76	$172.75	$172.80
Purchase #7	$56.82	9.250%	$62.0759	$62.08	$62.10	$62.10
7 purchase totals =	$896.17		$953.5409	$953.54	$953.50	$953.60