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	$172.25	11.810%	$192.5927	$192.59	$192.60	$192.60
Purchase #2	$225.86	4.449%	$235.9085	$235.91	$235.90	$235.90
Purchase #3	$113.52	5.285%	$119.5195	$119.52	$119.50	$119.50
Purchase #4	$81.50	6.321%	$86.6516	$86.65	$86.65	$86.70
Purchase #5	$124.86	5.142%	$131.2803	$131.28	$131.30	$131.30
Purchase #6	$71.79	9.370%	$78.5167	$78.52	$78.50	$78.50
Purchase #7	$203.26	8.452%	$220.4395	$220.44	$220.45	$220.40
7 purchase totals =	$993.04		$1,064.9088	$1,064.91	$1,064.90	$1,064.90