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	$111.82	7.684%	$120.4122	$120.41	$120.40	$120.40
Purchase #2	$162.98	5.327%	$171.6619	$171.66	$171.65	$171.70
Purchase #3	$93.89	7.244%	$100.6914	$100.69	$100.70	$100.70
Purchase #4	$54.74	12.571%	$61.6214	$61.62	$61.60	$61.60
Purchase #5	$69.36	9.795%	$76.1538	$76.15	$76.15	$76.20
Purchase #6	$149.35	10.438%	$164.9392	$164.94	$164.95	$164.90
Purchase #7	$180.62	5.166%	$189.9508	$189.95	$189.95	$190.00
7 purchase totals =	$822.76		$885.4307	$885.42	$885.40	$885.50