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	$201.91	6.387%	$214.806	$214.81	$214.80	$214.80
Purchase #2	$105.99	5.564%	$111.8873	$111.89	$111.90	$111.90
Purchase #3	$167.35	9.790%	$183.7336	$183.73	$183.75	$183.70
Purchase #4	$43.81	3.517%	$45.3508	$45.35	$45.35	$45.40
Purchase #5	$60.51	8.330%	$65.5505	$65.55	$65.55	$65.60
Purchase #6	$61.81	10.794%	$68.4818	$68.48	$68.50	$68.50
Purchase #7	$9.89	4.199%	$10.3053	$10.31	$10.30	$10.30
7 purchase totals =	$651.27		$700.1153	$700.12	$700.15	$700.20