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	$233.73	8.606%	$253.8448	$253.84	$253.85	$253.80
Purchase #2	$188.37	3.232%	$194.4581	$194.46	$194.45	$194.50
Purchase #3	$163.32	4.733%	$171.0499	$171.05	$171.05	$171.00
Purchase #4	$53.76	9.867%	$59.0645	$59.06	$59.05	$59.10
Purchase #5	$58.57	11.132%	$65.09	$65.09	$65.10	$65.10
Purchase #6	$44.27	3.366%	$45.7601	$45.76	$45.75	$45.80
Purchase #7	$140.72	11.433%	$156.8085	$156.81	$156.80	$156.80
7 purchase totals =	$882.74		$946.0759	$946.07	$946.05	$946.10