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	$219.35	4.338%	$228.8654	$228.87	$228.85	$228.90
Purchase #2	$45.80	11.717%	$51.1664	$51.17	$51.15	$51.20
Purchase #3	$151.90	4.599%	$158.8859	$158.89	$158.90	$158.90
Purchase #4	$105.46	6.373%	$112.181	$112.18	$112.20	$112.20
Purchase #5	$224.42	8.541%	$243.5877	$243.59	$243.60	$243.60
Purchase #6	$81.35	11.408%	$90.6304	$90.63	$90.65	$90.60
Purchase #7	$189.25	3.609%	$196.08	$196.08	$196.10	$196.10
7 purchase totals =	$1,017.53		$1,081.3968	$1,081.41	$1,081.45	$1,081.50