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	$67.96	13.865%	$77.3827	$77.38	$77.40	$77.40
Purchase #2	$48.38	11.507%	$53.9471	$53.95	$53.95	$53.90
Purchase #3	$112.60	5.226%	$118.4845	$118.48	$118.50	$118.50
Purchase #4	$73.86	13.103%	$83.5379	$83.54	$83.55	$83.50
Purchase #5	$62.47	5.335%	$65.8028	$65.80	$65.80	$65.80
Purchase #6	$126.54	6.218%	$134.4083	$134.41	$134.40	$134.40
Purchase #7	$178.83	10.139%	$196.9616	$196.96	$196.95	$197.00
7 purchase totals =	$670.64		$730.5249	$730.52	$730.55	$730.50