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	$65.42	10.554%	$72.3244	$72.32	$72.30	$72.30
Purchase #2	$160.39	5.772%	$169.6477	$169.65	$169.65	$169.60
Purchase #3	$85.38	11.280%	$95.0109	$95.01	$95.00	$95.00
Purchase #4	$192.75	11.213%	$214.3631	$214.36	$214.35	$214.40
Purchase #5	$37.39	11.236%	$41.5911	$41.59	$41.60	$41.60
Purchase #6	$122.61	7.201%	$131.4391	$131.44	$131.45	$131.40
Purchase #7	$211.55	6.643%	$225.6033	$225.60	$225.60	$225.60
7 purchase totals =	$875.49		$949.9796	$949.97	$949.95	$949.90