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	$91.51	9.150%	$99.8832	$99.88	$99.90	$99.90
Purchase #2	$193.75	7.183%	$207.6671	$207.67	$207.65	$207.70
Purchase #3	$70.45	5.677%	$74.4494	$74.45	$74.45	$74.40
Purchase #4	$25.85	10.719%	$28.6209	$28.62	$28.60	$28.60
Purchase #5	$56.57	5.653%	$59.7679	$59.77	$59.75	$59.80
Purchase #6	$120.32	3.131%	$124.0872	$124.09	$124.10	$124.10
Purchase #7	$100.27	3.600%	$103.8797	$103.88	$103.90	$103.90
7 purchase totals =	$658.72		$698.3554	$698.36	$698.35	$698.40