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	$69.32	12.585%	$78.0439	$78.04	$78.05	$78.00
Purchase #2	$138.62	6.625%	$147.8036	$147.80	$147.80	$147.80
Purchase #3	$11.30	3.687%	$11.7166	$11.72	$11.70	$11.70
Purchase #4	$247.43	9.319%	$270.488	$270.49	$270.50	$270.50
Purchase #5	$53.40	11.604%	$59.5965	$59.60	$59.60	$59.60
Purchase #6	$174.93	7.289%	$187.6806	$187.68	$187.70	$187.70
Purchase #7	$176.77	6.401%	$188.085	$188.09	$188.10	$188.10
7 purchase totals =	$871.77		$943.4142	$943.42	$943.45	$943.40