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	$108.73	8.222%	$117.6698	$117.67	$117.65	$117.70
Purchase #2	$134.49	9.582%	$147.3768	$147.38	$147.40	$147.40
Purchase #3	$8.83	13.396%	$10.0129	$10.01	$10.00	$10.00
Purchase #4	$106.55	4.493%	$111.3373	$111.34	$111.35	$111.30
Purchase #5	$145.38	4.467%	$151.8741	$151.87	$151.85	$151.90
Purchase #6	$86.70	13.152%	$98.1028	$98.10	$98.10	$98.10
Purchase #7	$155.66	12.503%	$175.1222	$175.12	$175.10	$175.10
7 purchase totals =	$746.34		$811.4959	$811.49	$811.45	$811.50