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	$165.78	9.487%	$181.5075	$181.51	$181.50	$181.50
Purchase #2	$244.40	11.483%	$272.4645	$272.46	$272.45	$272.50
Purchase #3	$156.54	5.208%	$164.6926	$164.69	$164.70	$164.70
Purchase #4	$184.52	4.210%	$192.2883	$192.29	$192.30	$192.30
Purchase #5	$18.38	11.444%	$20.4834	$20.48	$20.50	$20.50
Purchase #6	$249.64	6.428%	$265.6869	$265.69	$265.70	$265.70
Purchase #7	$74.82	9.145%	$81.6623	$81.66	$81.65	$81.70
7 purchase totals =	$1,094.08		$1,178.7855	$1,178.78	$1,178.80	$1,178.90