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	$107.85	3.166%	$111.2645	$111.26	$111.25	$111.30
Purchase #2	$230.38	10.807%	$255.2772	$255.28	$255.30	$255.30
Purchase #3	$141.48	6.109%	$150.123	$150.12	$150.10	$150.10
Purchase #4	$77.71	9.692%	$85.2417	$85.24	$85.25	$85.20
Purchase #5	$32.54	13.605%	$36.9671	$36.97	$36.95	$37.00
Purchase #6	$116.74	10.536%	$129.0397	$129.04	$129.05	$129.00
Purchase #7	$140.32	11.592%	$156.5859	$156.59	$156.60	$156.60
7 purchase totals =	$847.02		$924.4991	$924.50	$924.50	$924.50