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	$68.97	9.666%	$75.6366	$75.64	$75.65	$75.60
Purchase #2	$127.89	4.463%	$133.5977	$133.60	$133.60	$133.60
Purchase #3	$89.71	7.514%	$96.4508	$96.45	$96.45	$96.50
Purchase #4	$133.39	6.234%	$141.7055	$141.71	$141.70	$141.70
Purchase #5	$30.87	8.388%	$33.4594	$33.46	$33.45	$33.50
Purchase #6	$232.47	9.742%	$255.1172	$255.12	$255.10	$255.10
Purchase #7	$50.78	5.462%	$53.5536	$53.55	$53.55	$53.60
7 purchase totals =	$734.08		$789.5208	$789.53	$789.50	$789.60