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	$87.75	9.743%	$96.2995	$96.30	$96.30	$96.30
Purchase #2	$57.30	5.760%	$60.6005	$60.60	$60.60	$60.60
Purchase #3	$224.28	3.363%	$231.8225	$231.82	$231.80	$231.80
Purchase #4	$128.27	13.639%	$145.7647	$145.76	$145.75	$145.80
Purchase #5	$82.47	13.250%	$93.3973	$93.40	$93.40	$93.40
Purchase #6	$173.77	4.508%	$181.6036	$181.60	$181.60	$181.60
Purchase #7	$61.94	9.131%	$67.5957	$67.60	$67.60	$67.60
7 purchase totals =	$815.78		$877.0838	$877.08	$877.05	$877.10