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	$204.97	3.360%	$211.857	$211.86	$211.85	$211.90
Purchase #2	$73.54	13.533%	$83.4922	$83.49	$83.50	$83.50
Purchase #3	$10.64	5.413%	$11.2159	$11.22	$11.20	$11.20
Purchase #4	$19.77	12.188%	$22.1796	$22.18	$22.20	$22.20
Purchase #5	$199.61	10.671%	$220.9104	$220.91	$220.90	$220.90
Purchase #6	$46.38	12.236%	$52.0551	$52.06	$52.05	$52.10
Purchase #7	$42.81	5.452%	$45.144	$45.14	$45.15	$45.10
7 purchase totals =	$597.72		$646.8542	$646.86	$646.85	$646.90