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	$164.33	10.184%	$181.0654	$181.07	$181.05	$181.10
Purchase #2	$35.68	5.326%	$37.5803	$37.58	$37.60	$37.60
Purchase #3	$22.92	6.110%	$24.3204	$24.32	$24.30	$24.30
Purchase #4	$18.89	10.709%	$20.9129	$20.91	$20.90	$20.90
Purchase #5	$85.71	11.295%	$95.3909	$95.39	$95.40	$95.40
Purchase #6	$19.50	12.610%	$21.959	$21.96	$21.95	$22.00
Purchase #7	$12.45	8.322%	$13.4861	$13.49	$13.50	$13.50
7 purchase totals =	$359.48		$394.7150	$394.72	$394.70	$394.80