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	$229.72	9.333%	$251.1598	$251.16	$251.15	$251.20
Purchase #2	$70.32	11.576%	$78.4602	$78.46	$78.45	$78.50
Purchase #3	$72.62	9.157%	$79.2698	$79.27	$79.25	$79.30
Purchase #4	$39.80	10.294%	$43.897	$43.90	$43.90	$43.90
Purchase #5	$109.57	4.636%	$114.6497	$114.65	$114.65	$114.60
Purchase #6	$16.89	3.569%	$17.4928	$17.49	$17.50	$17.50
Purchase #7	$210.64	11.528%	$234.9226	$234.92	$234.90	$234.90
7 purchase totals =	$749.56		$819.8519	$819.85	$819.80	$819.90