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	$52.81	3.430%	$54.6214	$54.62	$54.60	$54.60
Purchase #2	$96.50	11.378%	$107.4798	$107.48	$107.50	$107.50
Purchase #3	$155.39	9.585%	$170.2841	$170.28	$170.30	$170.30
Purchase #4	$186.45	7.497%	$200.4282	$200.43	$200.45	$200.40
Purchase #5	$100.56	8.409%	$109.0161	$109.02	$109.00	$109.00
Purchase #6	$103.91	8.821%	$113.0759	$113.08	$113.10	$113.10
Purchase #7	$10.98	8.707%	$11.936	$11.94	$11.95	$11.90
7 purchase totals =	$706.60		$766.8415	$766.85	$766.90	$766.80