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	$151.47	10.406%	$167.232	$167.23	$167.25	$167.20
Purchase #2	$48.39	9.233%	$52.8578	$52.86	$52.85	$52.90
Purchase #3	$192.42	9.193%	$210.1092	$210.11	$210.10	$210.10
Purchase #4	$152.29	10.271%	$167.9317	$167.93	$167.95	$167.90
Purchase #5	$165.51	4.817%	$173.4826	$173.48	$173.50	$173.50
Purchase #6	$65.56	10.541%	$72.4707	$72.47	$72.45	$72.50
Purchase #7	$42.48	5.544%	$44.8351	$44.84	$44.85	$44.80
7 purchase totals =	$818.12		$888.9191	$888.92	$888.95	$888.90