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	$50.69	12.141%	$56.8443	$56.84	$56.85	$56.80
Purchase #2	$10.40	9.555%	$11.3937	$11.39	$11.40	$11.40
Purchase #3	$103.34	6.342%	$109.8938	$109.89	$109.90	$109.90
Purchase #4	$178.84	13.519%	$203.0174	$203.02	$203.00	$203.00
Purchase #5	$108.93	6.635%	$116.1575	$116.16	$116.15	$116.20
Purchase #6	$52.53	4.436%	$54.8602	$54.86	$54.85	$54.90
Purchase #7	$137.75	5.670%	$145.5604	$145.56	$145.55	$145.60
7 purchase totals =	$642.48		$697.7273	$697.72	$697.70	$697.80