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	$98.34	5.690%	$103.9355	$103.94	$103.95	$103.90
Purchase #2	$86.57	4.609%	$90.56	$90.56	$90.55	$90.60
Purchase #3	$182.95	9.179%	$199.743	$199.74	$199.75	$199.70
Purchase #4	$123.34	4.222%	$128.5474	$128.55	$128.55	$128.50
Purchase #5	$234.95	7.397%	$252.3293	$252.33	$252.35	$252.30
Purchase #6	$41.51	12.174%	$46.5634	$46.56	$46.55	$46.60
Purchase #7	$64.97	3.509%	$67.2498	$67.25	$67.25	$67.20
7 purchase totals =	$832.63		$888.9284	$888.93	$888.95	$888.80