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	$72.72	12.577%	$81.866	$81.87	$81.85	$81.90
Purchase #2	$225.36	12.307%	$253.0951	$253.10	$253.10	$253.10
Purchase #3	$105.56	4.521%	$110.3324	$110.33	$110.35	$110.30
Purchase #4	$129.32	4.235%	$134.7967	$134.80	$134.80	$134.80
Purchase #5	$90.54	3.822%	$94.0004	$94.00	$94.00	$94.00
Purchase #6	$171.76	5.581%	$181.3459	$181.35	$181.35	$181.30
Purchase #7	$138.31	10.731%	$153.152	$153.15	$153.15	$153.20
7 purchase totals =	$933.57		$1,008.5885	$1,008.60	$1,008.60	$1,008.60