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	$196.78	9.549%	$215.5705	$215.57	$215.55	$215.60
Purchase #2	$157.95	9.251%	$172.562	$172.56	$172.55	$172.60
Purchase #3	$151.30	8.792%	$164.6023	$164.60	$164.60	$164.60
Purchase #4	$10.50	12.700%	$11.8335	$11.83	$11.85	$11.80
Purchase #5	$170.76	10.719%	$189.0638	$189.06	$189.05	$189.10
Purchase #6	$41.41	10.608%	$45.8028	$45.80	$45.80	$45.80
Purchase #7	$27.46	11.271%	$30.555	$30.56	$30.55	$30.60
7 purchase totals =	$756.16		$829.9899	$829.98	$829.95	$830.10