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	$200.93	10.489%	$222.0055	$222.01	$222.00	$222.00
Purchase #2	$129.60	9.434%	$141.8265	$141.83	$141.85	$141.80
Purchase #3	$90.27	11.251%	$100.4263	$100.43	$100.45	$100.40
Purchase #4	$18.42	4.195%	$19.1927	$19.19	$19.20	$19.20
Purchase #5	$51.97	4.416%	$54.265	$54.27	$54.25	$54.30
Purchase #6	$151.74	5.427%	$159.9749	$159.97	$159.95	$160.00
Purchase #7	$220.65	12.424%	$248.0636	$248.06	$248.05	$248.10
7 purchase totals =	$863.58		$945.7545	$945.76	$945.75	$945.80