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	$53.94	9.125%	$58.862	$58.86	$58.85	$58.90
Purchase #2	$25.42	11.874%	$28.4384	$28.44	$28.45	$28.40
Purchase #3	$57.43	3.583%	$59.4877	$59.49	$59.50	$59.50
Purchase #4	$149.40	12.563%	$168.1691	$168.17	$168.15	$168.20
Purchase #5	$164.97	4.387%	$172.2072	$172.21	$172.20	$172.20
Purchase #6	$114.31	12.542%	$128.6468	$128.65	$128.65	$128.60
Purchase #7	$122.88	4.214%	$128.0582	$128.06	$128.05	$128.10
7 purchase totals =	$688.35		$743.8694	$743.88	$743.85	$743.90