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	$74.79	4.402%	$78.0823	$78.08	$78.10	$78.10
Purchase #2	$132.94	10.125%	$146.4002	$146.40	$146.40	$146.40
Purchase #3	$147.54	3.202%	$152.2642	$152.26	$152.25	$152.30
Purchase #4	$222.49	6.779%	$237.5726	$237.57	$237.55	$237.60
Purchase #5	$249.89	13.551%	$283.7526	$283.75	$283.75	$283.80
Purchase #6	$116.74	10.408%	$128.8903	$128.89	$128.90	$128.90
Purchase #7	$137.90	11.394%	$153.6123	$153.61	$153.60	$153.60
7 purchase totals =	$1,082.29		$1,180.5745	$1,180.56	$1,180.55	$1,180.70