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	$228.87	9.553%	$250.734	$250.73	$250.75	$250.70
Purchase #2	$160.74	12.847%	$181.3903	$181.39	$181.40	$181.40
Purchase #3	$119.90	10.156%	$132.077	$132.08	$132.10	$132.10
Purchase #4	$248.74	12.404%	$279.5937	$279.59	$279.60	$279.60
Purchase #5	$174.37	11.390%	$194.2307	$194.23	$194.25	$194.20
Purchase #6	$232.78	6.475%	$247.8525	$247.85	$247.85	$247.90
Purchase #7	$100.37	11.259%	$111.6707	$111.67	$111.65	$111.70
7 purchase totals =	$1,265.77		$1,397.5489	$1,397.54	$1,397.60	$1,397.60