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	$82.45	4.388%	$86.0679	$86.07	$86.05	$86.10
Purchase #2	$188.50	13.581%	$214.1002	$214.10	$214.10	$214.10
Purchase #3	$100.90	13.592%	$114.6143	$114.61	$114.60	$114.60
Purchase #4	$24.94	12.808%	$28.1343	$28.13	$28.15	$28.10
Purchase #5	$200.32	8.275%	$216.8965	$216.90	$216.90	$216.90
Purchase #6	$10.40	5.777%	$11.0008	$11.00	$11.00	$11.00
Purchase #7	$101.27	12.125%	$113.549	$113.55	$113.55	$113.50
7 purchase totals =	$708.78		$784.3630	$784.36	$784.35	$784.30