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	$208.41	6.730%	$222.436	$222.44	$222.45	$222.40
Purchase #2	$105.25	7.758%	$113.4153	$113.42	$113.40	$113.40
Purchase #3	$211.74	8.829%	$230.4345	$230.43	$230.45	$230.40
Purchase #4	$138.64	9.815%	$152.2475	$152.25	$152.25	$152.20
Purchase #5	$33.27	12.712%	$37.4993	$37.50	$37.50	$37.50
Purchase #6	$162.73	13.307%	$184.3845	$184.38	$184.40	$184.40
Purchase #7	$127.56	13.830%	$145.2015	$145.20	$145.20	$145.20
7 purchase totals =	$987.60		$1,085.6186	$1,085.62	$1,085.65	$1,085.50