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	$179.54	13.806%	$204.3273	$204.33	$204.35	$204.30
Purchase #2	$120.37	5.428%	$126.9037	$126.90	$126.90	$126.90
Purchase #3	$179.69	9.487%	$196.7372	$196.74	$196.75	$196.70
Purchase #4	$9.54	8.266%	$10.3286	$10.33	$10.35	$10.30
Purchase #5	$163.40	13.253%	$185.0554	$185.06	$185.05	$185.10
Purchase #6	$222.42	5.508%	$234.6709	$234.67	$234.65	$234.70
Purchase #7	$59.60	3.517%	$61.6961	$61.70	$61.70	$61.70
7 purchase totals =	$934.56		$1,019.7192	$1,019.73	$1,019.75	$1,019.70