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	$84.41	10.495%	$93.2688	$93.27	$93.25	$93.30
Purchase #2	$13.78	4.810%	$14.4428	$14.44	$14.45	$14.40
Purchase #3	$235.53	8.348%	$255.192	$255.19	$255.20	$255.20
Purchase #4	$87.52	13.744%	$99.5487	$99.55	$99.55	$99.50
Purchase #5	$82.36	9.869%	$90.4881	$90.49	$90.50	$90.50
Purchase #6	$190.94	12.413%	$214.6414	$214.64	$214.65	$214.60
Purchase #7	$156.92	10.659%	$173.6461	$173.65	$173.65	$173.60
7 purchase totals =	$851.46		$941.2279	$941.23	$941.25	$941.10