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	$29.89	8.512%	$32.4342	$32.43	$32.45	$32.40
Purchase #2	$45.85	5.744%	$48.4836	$48.48	$48.50	$48.50
Purchase #3	$65.69	13.683%	$74.6784	$74.68	$74.70	$74.70
Purchase #4	$217.25	13.210%	$245.9487	$245.95	$245.95	$245.90
Purchase #5	$196.25	11.812%	$219.4311	$219.43	$219.45	$219.40
Purchase #6	$233.65	4.447%	$244.0404	$244.04	$244.05	$244.00
Purchase #7	$136.40	12.448%	$153.3791	$153.38	$153.40	$153.40
7 purchase totals =	$924.98		$1,018.3955	$1,018.39	$1,018.50	$1,018.30