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	$143.94	5.664%	$152.0928	$152.09	$152.10	$152.10
Purchase #2	$194.68	11.308%	$216.6944	$216.69	$216.70	$216.70
Purchase #3	$179.49	6.130%	$190.4927	$190.49	$190.50	$190.50
Purchase #4	$215.34	10.446%	$237.8344	$237.83	$237.85	$237.80
Purchase #5	$167.35	12.763%	$188.7089	$188.71	$188.70	$188.70
Purchase #6	$242.27	5.335%	$255.1951	$255.20	$255.20	$255.20
Purchase #7	$131.50	10.712%	$145.5863	$145.59	$145.60	$145.60
7 purchase totals =	$1,274.57		$1,386.6046	$1,386.60	$1,386.65	$1,386.60