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	$99.72	5.793%	$105.4968	$105.50	$105.50	$105.50
Purchase #2	$197.85	13.671%	$224.8981	$224.90	$224.90	$224.90
Purchase #3	$152.51	13.627%	$173.2925	$173.29	$173.30	$173.30
Purchase #4	$120.70	3.469%	$124.8871	$124.89	$124.90	$124.90
Purchase #5	$135.58	6.564%	$144.4795	$144.48	$144.50	$144.50
Purchase #6	$230.85	10.734%	$255.6294	$255.63	$255.65	$255.60
Purchase #7	$91.51	5.541%	$96.5806	$96.58	$96.60	$96.60
7 purchase totals =	$1,028.72		$1,125.2640	$1,125.27	$1,125.35	$1,125.30