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	$223.83	11.737%	$250.1009	$250.10	$250.10	$250.10
Purchase #2	$214.90	12.186%	$241.0877	$241.09	$241.10	$241.10
Purchase #3	$10.69	3.465%	$11.0604	$11.06	$11.05	$11.10
Purchase #4	$213.90	4.692%	$223.9362	$223.94	$223.95	$223.90
Purchase #5	$16.69	6.849%	$17.8331	$17.83	$17.85	$17.80
Purchase #6	$178.55	12.347%	$200.5956	$200.60	$200.60	$200.60
Purchase #7	$145.51	11.681%	$162.507	$162.51	$162.50	$162.50
7 purchase totals =	$1,004.07		$1,107.1209	$1,107.13	$1,107.15	$1,107.10