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	$94.96	13.759%	$108.0255	$108.03	$108.05	$108.00
Purchase #2	$155.72	7.766%	$167.8132	$167.81	$167.80	$167.80
Purchase #3	$173.88	7.450%	$186.8341	$186.83	$186.85	$186.80
Purchase #4	$57.57	13.597%	$65.3978	$65.40	$65.40	$65.40
Purchase #5	$226.35	11.671%	$252.7673	$252.77	$252.75	$252.80
Purchase #6	$180.54	11.174%	$200.7135	$200.71	$200.70	$200.70
Purchase #7	$92.42	13.629%	$105.0159	$105.02	$105.00	$105.00
7 purchase totals =	$981.44		$1,086.5673	$1,086.57	$1,086.55	$1,086.50