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	$212.86	5.689%	$224.9696	$224.97	$224.95	$225.00
Purchase #2	$217.81	11.436%	$242.7188	$242.72	$242.70	$242.70
Purchase #3	$128.93	13.639%	$146.5148	$146.51	$146.50	$146.50
Purchase #4	$17.59	8.111%	$19.0167	$19.02	$19.00	$19.00
Purchase #5	$174.66	9.697%	$191.5968	$191.60	$191.60	$191.60
Purchase #6	$36.56	4.570%	$38.2308	$38.23	$38.25	$38.20
Purchase #7	$69.27	13.858%	$78.8694	$78.87	$78.85	$78.90
7 purchase totals =	$857.68		$941.9169	$941.92	$941.85	$941.90