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	$63.32	3.519%	$65.5482	$65.55	$65.55	$65.50
Purchase #2	$27.71	11.267%	$30.8321	$30.83	$30.85	$30.80
Purchase #3	$128.59	13.137%	$145.4829	$145.48	$145.50	$145.50
Purchase #4	$19.66	6.279%	$20.8945	$20.89	$20.90	$20.90
Purchase #5	$59.42	6.531%	$63.3007	$63.30	$63.30	$63.30
Purchase #6	$144.38	8.355%	$156.4429	$156.44	$156.45	$156.40
Purchase #7	$10.90	10.329%	$12.0259	$12.03	$12.05	$12.00
7 purchase totals =	$453.98		$494.5272	$494.52	$494.60	$494.40