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	$93.43	11.125%	$103.8241	$103.82	$103.80	$103.80
Purchase #2	$161.50	12.185%	$181.1788	$181.18	$181.20	$181.20
Purchase #3	$25.51	10.112%	$28.0896	$28.09	$28.10	$28.10
Purchase #4	$210.88	8.178%	$228.1258	$228.13	$228.15	$228.10
Purchase #5	$116.38	6.273%	$123.6805	$123.68	$123.70	$123.70
Purchase #6	$60.51	11.404%	$67.4106	$67.41	$67.40	$67.40
Purchase #7	$127.56	3.716%	$132.3001	$132.30	$132.30	$132.30
7 purchase totals =	$795.77		$864.6095	$864.61	$864.65	$864.60