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	$128.58	6.467%	$136.8953	$136.90	$136.90	$136.90
Purchase #2	$123.40	9.142%	$134.6812	$134.68	$134.70	$134.70
Purchase #3	$105.76	11.687%	$118.1202	$118.12	$118.10	$118.10
Purchase #4	$149.33	8.433%	$161.923	$161.92	$161.90	$161.90
Purchase #5	$117.32	8.505%	$127.2981	$127.30	$127.30	$127.30
Purchase #6	$167.78	4.833%	$175.8888	$175.89	$175.90	$175.90
Purchase #7	$194.40	5.513%	$205.1173	$205.12	$205.10	$205.10
7 purchase totals =	$986.57		$1,059.9239	$1,059.93	$1,059.90	$1,059.90