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	$215.32	6.750%	$229.8541	$229.85	$229.85	$229.90
Purchase #2	$219.66	11.466%	$244.8462	$244.85	$244.85	$244.80
Purchase #3	$114.78	3.439%	$118.7273	$118.73	$118.75	$118.70
Purchase #4	$187.26	4.865%	$196.3702	$196.37	$196.35	$196.40
Purchase #5	$87.68	5.743%	$92.7155	$92.72	$92.70	$92.70
Purchase #6	$93.92	8.444%	$101.8506	$101.85	$101.85	$101.90
Purchase #7	$184.60	11.342%	$205.5373	$205.54	$205.55	$205.50
7 purchase totals =	$1,103.22		$1,189.9012	$1,189.91	$1,189.90	$1,189.90