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	$148.77	6.500%	$158.4401	$158.44	$158.45	$158.40
Purchase #2	$138.74	10.500%	$153.3077	$153.31	$153.30	$153.30
Purchase #3	$120.49	9.396%	$131.8112	$131.81	$131.80	$131.80
Purchase #4	$60.27	12.604%	$67.8664	$67.87	$67.85	$67.90
Purchase #5	$101.31	4.704%	$106.0756	$106.08	$106.10	$106.10
Purchase #6	$86.96	5.172%	$91.4576	$91.46	$91.45	$91.50
Purchase #7	$144.57	9.193%	$157.8603	$157.86	$157.85	$157.90
7 purchase totals =	$801.11		$866.8189	$866.83	$866.80	$866.90