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	$81.98	4.821%	$85.9323	$85.93	$85.95	$85.90
Purchase #2	$72.41	4.412%	$75.6047	$75.60	$75.60	$75.60
Purchase #3	$52.87	9.445%	$57.8636	$57.86	$57.85	$57.90
Purchase #4	$138.46	5.535%	$146.1238	$146.12	$146.10	$146.10
Purchase #5	$22.95	9.786%	$25.1959	$25.20	$25.20	$25.20
Purchase #6	$120.90	5.403%	$127.4322	$127.43	$127.45	$127.40
Purchase #7	$13.70	5.572%	$14.4634	$14.46	$14.45	$14.50
7 purchase totals =	$503.27		$532.6159	$532.60	$532.60	$532.60