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	$214.81	10.461%	$237.2813	$237.28	$237.30	$237.30
Purchase #2	$115.54	7.471%	$124.172	$124.17	$124.15	$124.20
Purchase #3	$73.77	7.744%	$79.4827	$79.48	$79.50	$79.50
Purchase #4	$103.90	7.598%	$111.7943	$111.79	$111.80	$111.80
Purchase #5	$42.41	9.346%	$46.3736	$46.37	$46.35	$46.40
Purchase #6	$170.38	11.289%	$189.6142	$189.61	$189.60	$189.60
Purchase #7	$53.54	10.225%	$59.0145	$59.01	$59.00	$59.00
7 purchase totals =	$774.35		$847.7326	$847.71	$847.70	$847.80