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	$156.48	10.527%	$172.9526	$172.95	$172.95	$173.00
Purchase #2	$89.70	5.167%	$94.3348	$94.33	$94.35	$94.30
Purchase #3	$175.98	3.219%	$181.6448	$181.64	$181.65	$181.60
Purchase #4	$124.57	6.118%	$132.1912	$132.19	$132.20	$132.20
Purchase #5	$231.47	5.234%	$243.5851	$243.59	$243.60	$243.60
Purchase #6	$156.96	5.406%	$165.4453	$165.45	$165.45	$165.40
Purchase #7	$91.97	4.182%	$95.8162	$95.82	$95.80	$95.80
7 purchase totals =	$1,027.13		$1,085.9700	$1,085.97	$1,086.00	$1,085.90