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	$160.54	5.256%	$168.978	$168.98	$169.00	$169.00
Purchase #2	$44.26	5.150%	$46.5394	$46.54	$46.55	$46.50
Purchase #3	$173.94	11.115%	$193.2734	$193.27	$193.25	$193.30
Purchase #4	$247.58	13.549%	$281.1246	$281.12	$281.10	$281.10
Purchase #5	$80.84	12.498%	$90.9434	$90.94	$90.95	$90.90
Purchase #6	$31.86	5.745%	$33.6904	$33.69	$33.70	$33.70
Purchase #7	$64.38	3.120%	$66.3887	$66.39	$66.40	$66.40
7 purchase totals =	$803.40		$880.9379	$880.93	$880.95	$880.90