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	$69.45	3.568%	$71.928	$71.93	$71.95	$71.90
Purchase #2	$59.85	10.739%	$66.2773	$66.28	$66.30	$66.30
Purchase #3	$70.53	4.374%	$73.615	$73.62	$73.60	$73.60
Purchase #4	$105.43	3.342%	$108.9535	$108.95	$108.95	$109.00
Purchase #5	$135.57	7.182%	$145.3066	$145.31	$145.30	$145.30
Purchase #6	$75.53	3.649%	$78.2861	$78.29	$78.30	$78.30
Purchase #7	$154.32	5.225%	$162.3832	$162.38	$162.40	$162.40
7 purchase totals =	$670.68		$706.7497	$706.76	$706.80	$706.80