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	$168.83	9.210%	$184.3792	$184.38	$184.40	$184.40
Purchase #2	$104.48	7.321%	$112.129	$112.13	$112.15	$112.10
Purchase #3	$53.62	12.437%	$60.2887	$60.29	$60.30	$60.30
Purchase #4	$147.56	6.718%	$157.4731	$157.47	$157.45	$157.50
Purchase #5	$116.89	12.480%	$131.4779	$131.48	$131.50	$131.50
Purchase #6	$154.95	13.603%	$176.0278	$176.03	$176.05	$176.00
Purchase #7	$66.42	8.802%	$72.2663	$72.27	$72.25	$72.30
7 purchase totals =	$812.75		$894.0420	$894.05	$894.10	$894.10