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	$151.32	11.553%	$168.802	$168.80	$168.80	$168.80
Purchase #2	$127.51	6.872%	$136.2725	$136.27	$136.25	$136.30
Purchase #3	$173.90	6.627%	$185.4244	$185.42	$185.40	$185.40
Purchase #4	$132.48	8.611%	$143.8879	$143.89	$143.90	$143.90
Purchase #5	$138.51	7.461%	$148.8442	$148.84	$148.85	$148.80
Purchase #6	$141.71	8.177%	$153.2976	$153.30	$153.30	$153.30
Purchase #7	$79.44	7.207%	$85.1652	$85.17	$85.15	$85.20
7 purchase totals =	$944.87		$1,021.6938	$1,021.69	$1,021.65	$1,021.70