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	$167.27	10.798%	$185.3318	$185.33	$185.35	$185.30
Purchase #2	$168.80	9.422%	$184.7043	$184.70	$184.70	$184.70
Purchase #3	$200.39	11.177%	$222.7876	$222.79	$222.80	$222.80
Purchase #4	$89.33	6.429%	$95.073	$95.07	$95.05	$95.10
Purchase #5	$179.35	8.852%	$195.2261	$195.23	$195.25	$195.20
Purchase #6	$133.55	12.571%	$150.3386	$150.34	$150.35	$150.30
Purchase #7	$28.34	13.627%	$32.2019	$32.20	$32.20	$32.20
7 purchase totals =	$967.03		$1,065.6633	$1,065.66	$1,065.70	$1,065.60