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	$94.42	6.792%	$100.833	$100.83	$100.85	$100.80
Purchase #2	$51.85	7.404%	$55.689	$55.69	$55.70	$55.70
Purchase #3	$44.43	13.628%	$50.4849	$50.48	$50.50	$50.50
Purchase #4	$150.98	4.853%	$158.3071	$158.31	$158.30	$158.30
Purchase #5	$199.25	5.715%	$210.6371	$210.64	$210.65	$210.60
Purchase #6	$133.32	8.800%	$145.0522	$145.05	$145.05	$145.10
Purchase #7	$23.35	3.269%	$24.1133	$24.11	$24.10	$24.10
7 purchase totals =	$697.60		$745.1166	$745.11	$745.15	$745.10