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	$115.55	11.364%	$128.6811	$128.68	$128.70	$128.70
Purchase #2	$97.44	10.725%	$107.8904	$107.89	$107.90	$107.90
Purchase #3	$130.65	5.578%	$137.9377	$137.94	$137.95	$137.90
Purchase #4	$165.33	3.588%	$171.262	$171.26	$171.25	$171.30
Purchase #5	$61.64	4.579%	$64.4625	$64.46	$64.45	$64.50
Purchase #6	$80.78	12.114%	$90.5657	$90.57	$90.55	$90.60
Purchase #7	$245.57	9.451%	$268.7788	$268.78	$268.80	$268.80
7 purchase totals =	$896.96		$969.5782	$969.58	$969.60	$969.70