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	$167.88	10.478%	$185.4705	$185.47	$185.45	$185.50
Purchase #2	$35.60	7.338%	$38.2123	$38.21	$38.20	$38.20
Purchase #3	$154.39	12.141%	$173.1345	$173.13	$173.15	$173.10
Purchase #4	$174.69	6.463%	$185.9802	$185.98	$186.00	$186.00
Purchase #5	$217.66	4.335%	$227.0956	$227.10	$227.10	$227.10
Purchase #6	$159.45	13.575%	$181.0953	$181.10	$181.10	$181.10
Purchase #7	$83.90	7.850%	$90.4862	$90.49	$90.50	$90.50
7 purchase totals =	$993.57		$1,081.4746	$1,081.48	$1,081.50	$1,081.50