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	$42.34	9.715%	$46.4533	$46.45	$46.45	$46.50
Purchase #2	$141.98	3.261%	$146.61	$146.61	$146.60	$146.60
Purchase #3	$138.25	7.133%	$148.1114	$148.11	$148.10	$148.10
Purchase #4	$10.98	9.740%	$12.0495	$12.05	$12.05	$12.00
Purchase #5	$59.96	4.141%	$62.4429	$62.44	$62.45	$62.40
Purchase #6	$208.31	10.227%	$229.6139	$229.61	$229.60	$229.60
Purchase #7	$118.39	12.239%	$132.8798	$132.88	$132.90	$132.90
7 purchase totals =	$720.21		$778.1608	$778.15	$778.15	$778.10