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	$195.77	11.540%	$218.3619	$218.36	$218.35	$218.40
Purchase #2	$72.58	7.740%	$78.1977	$78.20	$78.20	$78.20
Purchase #3	$31.28	10.149%	$34.4546	$34.45	$34.45	$34.50
Purchase #4	$14.65	5.848%	$15.5067	$15.51	$15.50	$15.50
Purchase #5	$135.31	4.642%	$141.5911	$141.59	$141.60	$141.60
Purchase #6	$162.95	3.617%	$168.8439	$168.84	$168.85	$168.80
Purchase #7	$73.58	10.183%	$81.0727	$81.07	$81.05	$81.10
7 purchase totals =	$686.12		$738.0286	$738.02	$738.00	$738.10