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	$168.91	9.358%	$184.7166	$184.72	$184.70	$184.70
Purchase #2	$116.27	5.670%	$122.8625	$122.86	$122.85	$122.90
Purchase #3	$197.96	10.690%	$219.1219	$219.12	$219.10	$219.10
Purchase #4	$179.86	3.146%	$185.5184	$185.52	$185.50	$185.50
Purchase #5	$57.37	13.604%	$65.1746	$65.17	$65.15	$65.20
Purchase #6	$81.65	10.643%	$90.34	$90.34	$90.35	$90.30
Purchase #7	$62.89	10.149%	$69.2727	$69.27	$69.25	$69.30
7 purchase totals =	$864.91		$937.0067	$937.00	$936.90	$937.00