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	$161.69	7.318%	$173.5225	$173.52	$173.50	$173.50
Purchase #2	$26.38	3.523%	$27.3094	$27.31	$27.30	$27.30
Purchase #3	$68.38	6.277%	$72.6722	$72.67	$72.65	$72.70
Purchase #4	$41.74	8.634%	$45.3438	$45.34	$45.35	$45.30
Purchase #5	$196.72	7.798%	$212.0602	$212.06	$212.05	$212.10
Purchase #6	$163.63	8.862%	$178.1309	$178.13	$178.15	$178.10
Purchase #7	$17.90	5.566%	$18.8963	$18.90	$18.90	$18.90
7 purchase totals =	$676.44		$727.9353	$727.93	$727.90	$727.90