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	$58.45	6.553%	$62.2802	$62.28	$62.30	$62.30
Purchase #2	$247.97	3.163%	$255.8133	$255.81	$255.80	$255.80
Purchase #3	$120.49	6.665%	$128.5207	$128.52	$128.50	$128.50
Purchase #4	$118.33	7.366%	$127.0462	$127.05	$127.05	$127.00
Purchase #5	$199.72	11.526%	$222.7397	$222.74	$222.75	$222.70
Purchase #6	$52.64	13.128%	$59.5506	$59.55	$59.55	$59.60
Purchase #7	$36.41	3.166%	$37.5627	$37.56	$37.55	$37.60
7 purchase totals =	$834.01		$893.5134	$893.51	$893.50	$893.50