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	$103.44	3.302%	$106.8556	$106.86	$106.85	$106.90
Purchase #2	$41.47	8.665%	$45.0634	$45.06	$45.05	$45.10
Purchase #3	$203.93	13.230%	$230.9099	$230.91	$230.90	$230.90
Purchase #4	$136.87	12.196%	$153.5627	$153.56	$153.55	$153.60
Purchase #5	$28.89	12.855%	$32.6038	$32.60	$32.60	$32.60
Purchase #6	$33.42	7.722%	$36.0007	$36.00	$36.00	$36.00
Purchase #7	$89.52	13.304%	$101.4297	$101.43	$101.45	$101.40
7 purchase totals =	$637.54		$706.4258	$706.42	$706.40	$706.50