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	$102.81	5.717%	$108.6876	$108.69	$108.70	$108.70
Purchase #2	$164.59	4.659%	$172.2582	$172.26	$172.25	$172.30
Purchase #3	$230.73	13.717%	$262.3792	$262.38	$262.40	$262.40
Purchase #4	$122.38	8.191%	$132.4041	$132.40	$132.40	$132.40
Purchase #5	$33.72	9.722%	$36.9983	$37.00	$37.00	$37.00
Purchase #6	$187.41	13.131%	$212.0188	$212.02	$212.00	$212.00
Purchase #7	$155.61	4.160%	$162.0834	$162.08	$162.10	$162.10
7 purchase totals =	$997.25		$1,086.8296	$1,086.83	$1,086.85	$1,086.90