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	$52.56	13.377%	$59.591	$59.59	$59.60	$59.60
Purchase #2	$160.38	4.812%	$168.0975	$168.10	$168.10	$168.10
Purchase #3	$77.29	11.662%	$86.3036	$86.30	$86.30	$86.30
Purchase #4	$43.93	12.525%	$49.4322	$49.43	$49.45	$49.40
Purchase #5	$139.79	13.278%	$158.3513	$158.35	$158.35	$158.40
Purchase #6	$201.70	11.230%	$224.3509	$224.35	$224.35	$224.40
Purchase #7	$235.71	12.246%	$264.575	$264.58	$264.60	$264.60
7 purchase totals =	$911.36		$1,010.7015	$1,010.70	$1,010.75	$1,010.80