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	$46.56	8.594%	$50.5614	$50.56	$50.55	$50.60
Purchase #2	$114.62	9.838%	$125.8963	$125.90	$125.90	$125.90
Purchase #3	$109.62	4.811%	$114.8938	$114.89	$114.90	$114.90
Purchase #4	$89.45	5.777%	$94.6175	$94.62	$94.60	$94.60
Purchase #5	$89.83	10.265%	$99.051	$99.05	$99.05	$99.10
Purchase #6	$12.99	8.347%	$14.0743	$14.07	$14.05	$14.10
Purchase #7	$40.94	13.279%	$46.3764	$46.38	$46.40	$46.40
7 purchase totals =	$504.01		$545.4707	$545.47	$545.45	$545.60