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	$179.64	11.540%	$200.3705	$200.37	$200.35	$200.40
Purchase #2	$58.30	8.643%	$63.3389	$63.34	$63.35	$63.30
Purchase #3	$229.76	10.708%	$254.3627	$254.36	$254.35	$254.40
Purchase #4	$78.27	5.342%	$82.4512	$82.45	$82.45	$82.50
Purchase #5	$157.32	7.108%	$168.5023	$168.50	$168.50	$168.50
Purchase #6	$17.75	9.241%	$19.3903	$19.39	$19.40	$19.40
Purchase #7	$161.94	4.769%	$169.6629	$169.66	$169.65	$169.70
7 purchase totals =	$882.98		$958.0788	$958.07	$958.05	$958.20