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	$167.69	6.441%	$178.4909	$178.49	$178.50	$178.50
Purchase #2	$238.71	7.189%	$255.8709	$255.87	$255.85	$255.90
Purchase #3	$105.98	5.637%	$111.9541	$111.95	$111.95	$112.00
Purchase #4	$146.34	3.404%	$151.3214	$151.32	$151.30	$151.30
Purchase #5	$16.72	7.814%	$18.0265	$18.03	$18.05	$18.00
Purchase #6	$158.36	3.605%	$164.0689	$164.07	$164.05	$164.10
Purchase #7	$145.55	11.771%	$162.6827	$162.68	$162.70	$162.70
7 purchase totals =	$979.35		$1,042.4154	$1,042.41	$1,042.40	$1,042.50