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	$97.60	11.694%	$109.0133	$109.01	$109.00	$109.00
Purchase #2	$167.67	11.223%	$186.4876	$186.49	$186.50	$186.50
Purchase #3	$138.73	11.266%	$154.3593	$154.36	$154.35	$154.40
Purchase #4	$240.94	5.849%	$255.0326	$255.03	$255.05	$255.00
Purchase #5	$122.27	10.559%	$135.1805	$135.18	$135.20	$135.20
Purchase #6	$40.42	8.648%	$43.9155	$43.92	$43.90	$43.90
Purchase #7	$103.55	7.701%	$111.5244	$111.52	$111.50	$111.50
7 purchase totals =	$911.18		$995.5132	$995.51	$995.50	$995.50