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	$144.90	8.281%	$156.8992	$156.90	$156.90	$156.90
Purchase #2	$196.39	7.658%	$211.4295	$211.43	$211.45	$211.40
Purchase #3	$148.78	6.530%	$158.4953	$158.50	$158.50	$158.50
Purchase #4	$59.37	6.596%	$63.286	$63.29	$63.30	$63.30
Purchase #5	$19.31	10.612%	$21.3592	$21.36	$21.35	$21.40
Purchase #6	$116.26	7.412%	$124.8772	$124.88	$124.90	$124.90
Purchase #7	$140.56	5.712%	$148.5888	$148.59	$148.60	$148.60
7 purchase totals =	$825.57		$884.9352	$884.95	$885.00	$885.00