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	$89.54	13.524%	$101.6494	$101.65	$101.65	$101.60
Purchase #2	$172.44	6.735%	$184.0538	$184.05	$184.05	$184.10
Purchase #3	$141.29	9.219%	$154.3155	$154.32	$154.30	$154.30
Purchase #4	$36.93	9.676%	$40.5033	$40.50	$40.50	$40.50
Purchase #5	$91.81	4.298%	$95.756	$95.76	$95.75	$95.80
Purchase #6	$17.69	13.525%	$20.0826	$20.08	$20.10	$20.10
Purchase #7	$33.82	3.756%	$35.0903	$35.09	$35.10	$35.10
7 purchase totals =	$583.52		$631.4509	$631.45	$631.45	$631.50