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	$233.46	7.766%	$251.5905	$251.59	$251.60	$251.60
Purchase #2	$132.63	13.288%	$150.2539	$150.25	$150.25	$150.30
Purchase #3	$137.74	5.510%	$145.3295	$145.33	$145.35	$145.30
Purchase #4	$90.45	13.574%	$102.7277	$102.73	$102.75	$102.70
Purchase #5	$54.66	12.185%	$61.3203	$61.32	$61.30	$61.30
Purchase #6	$160.48	5.125%	$168.7046	$168.70	$168.70	$168.70
Purchase #7	$73.54	4.672%	$76.9758	$76.98	$77.00	$77.00
7 purchase totals =	$882.96		$956.9023	$956.90	$956.95	$956.90