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	$68.73	12.115%	$77.0566	$77.06	$77.05	$77.10
Purchase #2	$111.83	10.494%	$123.5654	$123.57	$123.55	$123.60
Purchase #3	$163.68	4.585%	$171.1847	$171.18	$171.20	$171.20
Purchase #4	$153.93	3.618%	$159.4992	$159.50	$159.50	$159.50
Purchase #5	$30.66	5.237%	$32.2657	$32.27	$32.25	$32.30
Purchase #6	$247.27	11.426%	$275.5231	$275.52	$275.50	$275.50
Purchase #7	$120.69	5.858%	$127.76	$127.76	$127.75	$127.80
7 purchase totals =	$896.79		$966.8547	$966.86	$966.80	$967.00