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	$69.37	4.813%	$72.7088	$72.71	$72.70	$72.70
Purchase #2	$113.44	10.131%	$124.9326	$124.93	$124.95	$124.90
Purchase #3	$117.71	5.722%	$124.4454	$124.45	$124.45	$124.40
Purchase #4	$197.34	9.668%	$216.4188	$216.42	$216.40	$216.40
Purchase #5	$60.71	10.744%	$67.2327	$67.23	$67.25	$67.20
Purchase #6	$64.93	3.318%	$67.0844	$67.08	$67.10	$67.10
Purchase #7	$65.34	10.428%	$72.1537	$72.15	$72.15	$72.20
7 purchase totals =	$688.84		$744.9764	$744.97	$745.00	$744.90