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	$197.90	6.872%	$211.4997	$211.50	$211.50	$211.50
Purchase #2	$184.87	10.739%	$204.7232	$204.72	$204.70	$204.70
Purchase #3	$212.91	6.187%	$226.0827	$226.08	$226.10	$226.10
Purchase #4	$59.33	13.828%	$67.5342	$67.53	$67.55	$67.50
Purchase #5	$148.96	5.127%	$156.5972	$156.60	$156.60	$156.60
Purchase #6	$215.50	3.785%	$223.6567	$223.66	$223.65	$223.70
Purchase #7	$50.35	12.200%	$56.4927	$56.49	$56.50	$56.50
7 purchase totals =	$1,069.82		$1,146.5864	$1,146.58	$1,146.60	$1,146.60