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	$101.35	11.415%	$112.9191	$112.92	$112.90	$112.90
Purchase #2	$75.25	4.268%	$78.4617	$78.46	$78.45	$78.50
Purchase #3	$65.89	3.366%	$68.1079	$68.11	$68.10	$68.10
Purchase #4	$164.29	4.246%	$171.2658	$171.27	$171.25	$171.30
Purchase #5	$55.33	9.491%	$60.5814	$60.58	$60.60	$60.60
Purchase #6	$95.27	4.468%	$99.5267	$99.53	$99.55	$99.50
Purchase #7	$133.87	7.365%	$143.7295	$143.73	$143.75	$143.70
7 purchase totals =	$691.25		$734.5921	$734.60	$734.60	$734.60