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	$172.49	6.187%	$183.162	$183.16	$183.15	$183.20
Purchase #2	$130.51	10.442%	$144.1379	$144.14	$144.15	$144.10
Purchase #3	$100.63	4.518%	$105.1765	$105.18	$105.20	$105.20
Purchase #4	$106.31	11.378%	$118.406	$118.41	$118.40	$118.40
Purchase #5	$83.82	9.726%	$91.9723	$91.97	$91.95	$92.00
Purchase #6	$200.62	13.663%	$228.0307	$228.03	$228.05	$228.00
Purchase #7	$129.83	12.103%	$145.5433	$145.54	$145.55	$145.50
7 purchase totals =	$924.21		$1,016.4287	$1,016.43	$1,016.45	$1,016.40