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	$39.90	13.246%	$45.1852	$45.19	$45.20	$45.20
Purchase #2	$45.77	13.264%	$51.8409	$51.84	$51.85	$51.80
Purchase #3	$26.92	9.726%	$29.5382	$29.54	$29.55	$29.50
Purchase #4	$74.71	7.581%	$80.3738	$80.37	$80.35	$80.40
Purchase #5	$76.70	11.497%	$85.5182	$85.52	$85.50	$85.50
Purchase #6	$174.75	7.271%	$187.4561	$187.46	$187.45	$187.50
Purchase #7	$198.94	10.337%	$219.5044	$219.50	$219.50	$219.50
7 purchase totals =	$637.69		$699.4168	$699.42	$699.40	$699.40