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	$102.74	8.499%	$111.4719	$111.47	$111.45	$111.50
Purchase #2	$89.73	9.220%	$98.0031	$98.00	$98.00	$98.00
Purchase #3	$239.72	9.653%	$262.8602	$262.86	$262.85	$262.90
Purchase #4	$215.28	3.451%	$222.7093	$222.71	$222.70	$222.70
Purchase #5	$235.69	3.560%	$244.0806	$244.08	$244.10	$244.10
Purchase #6	$203.30	8.232%	$220.0357	$220.04	$220.05	$220.00
Purchase #7	$99.77	5.635%	$105.392	$105.39	$105.40	$105.40
7 purchase totals =	$1,186.23		$1,264.5528	$1,264.55	$1,264.55	$1,264.60