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	$106.84	9.141%	$116.6062	$116.61	$116.60	$116.60
Purchase #2	$88.64	13.223%	$100.3609	$100.36	$100.35	$100.40
Purchase #3	$100.71	10.500%	$111.2846	$111.28	$111.30	$111.30
Purchase #4	$71.85	9.459%	$78.6463	$78.65	$78.65	$78.60
Purchase #5	$73.31	11.798%	$81.9591	$81.96	$81.95	$82.00
Purchase #6	$20.49	9.441%	$22.4245	$22.42	$22.40	$22.40
Purchase #7	$134.89	5.384%	$142.1525	$142.15	$142.15	$142.20
7 purchase totals =	$596.73		$653.4341	$653.43	$653.40	$653.50