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	$224.25	4.581%	$234.5229	$234.52	$234.50	$234.50
Purchase #2	$170.87	4.616%	$178.7574	$178.76	$178.75	$178.80
Purchase #3	$43.87	12.308%	$49.2695	$49.27	$49.25	$49.30
Purchase #4	$227.52	10.830%	$252.1604	$252.16	$252.15	$252.20
Purchase #5	$167.51	12.298%	$188.1104	$188.11	$188.10	$188.10
Purchase #6	$84.58	6.553%	$90.1225	$90.12	$90.10	$90.10
Purchase #7	$100.74	4.591%	$105.365	$105.37	$105.35	$105.40
7 purchase totals =	$1,019.34		$1,098.3081	$1,098.31	$1,098.20	$1,098.40