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	$222.46	6.748%	$237.4716	$237.47	$237.45	$237.50
Purchase #2	$143.25	5.554%	$151.2061	$151.21	$151.20	$151.20
Purchase #3	$197.91	9.441%	$216.5947	$216.59	$216.60	$216.60
Purchase #4	$172.98	3.465%	$178.9738	$178.97	$178.95	$179.00
Purchase #5	$48.26	13.805%	$54.9223	$54.92	$54.90	$54.90
Purchase #6	$23.59	3.353%	$24.381	$24.38	$24.40	$24.40
Purchase #7	$139.25	9.263%	$152.1487	$152.15	$152.15	$152.10
7 purchase totals =	$947.70		$1,015.6982	$1,015.69	$1,015.65	$1,015.70