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	$138.55	12.543%	$155.9283	$155.93	$155.95	$155.90
Purchase #2	$202.91	9.856%	$222.9088	$222.91	$222.90	$222.90
Purchase #3	$88.38	4.407%	$92.2749	$92.27	$92.25	$92.30
Purchase #4	$202.83	13.853%	$230.928	$230.93	$230.95	$230.90
Purchase #5	$148.40	6.320%	$157.7789	$157.78	$157.80	$157.80
Purchase #6	$133.98	11.133%	$148.896	$148.90	$148.90	$148.90
Purchase #7	$109.93	8.252%	$119.0014	$119.00	$119.00	$119.00
7 purchase totals =	$1,024.98		$1,127.7163	$1,127.72	$1,127.75	$1,127.70