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	$237.78	13.321%	$269.4547	$269.45	$269.45	$269.50
Purchase #2	$55.80	6.584%	$59.4739	$59.47	$59.45	$59.50
Purchase #3	$169.54	5.444%	$178.7698	$178.77	$178.75	$178.80
Purchase #4	$57.99	5.683%	$61.2856	$61.29	$61.30	$61.30
Purchase #5	$146.67	12.518%	$165.0302	$165.03	$165.05	$165.00
Purchase #6	$49.45	9.114%	$53.9569	$53.96	$53.95	$54.00
Purchase #7	$95.49	12.298%	$107.2334	$107.23	$107.25	$107.20
7 purchase totals =	$812.72		$895.2045	$895.20	$895.20	$895.30