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	$90.25	12.555%	$101.5809	$101.58	$101.60	$101.60
Purchase #2	$152.35	11.661%	$170.1155	$170.12	$170.10	$170.10
Purchase #3	$210.83	5.735%	$222.9211	$222.92	$222.90	$222.90
Purchase #4	$117.32	12.731%	$132.256	$132.26	$132.25	$132.30
Purchase #5	$44.69	4.193%	$46.5639	$46.56	$46.55	$46.60
Purchase #6	$235.38	6.412%	$250.4726	$250.47	$250.45	$250.50
Purchase #7	$118.40	3.476%	$122.5156	$122.52	$122.50	$122.50
7 purchase totals =	$969.22		$1,046.4256	$1,046.43	$1,046.35	$1,046.50