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	$174.60	9.348%	$190.9216	$190.92	$190.90	$190.90
Purchase #2	$81.72	10.145%	$90.0105	$90.01	$90.00	$90.00
Purchase #3	$10.39	8.512%	$11.2744	$11.27	$11.25	$11.30
Purchase #4	$147.92	4.303%	$154.285	$154.29	$154.30	$154.30
Purchase #5	$176.47	13.500%	$200.2935	$200.29	$200.30	$200.30
Purchase #6	$101.44	5.535%	$107.0547	$107.05	$107.05	$107.10
Purchase #7	$94.73	11.385%	$105.515	$105.52	$105.50	$105.50
7 purchase totals =	$787.27		$859.3547	$859.35	$859.30	$859.40