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	$200.53	12.646%	$225.889	$225.89	$225.90	$225.90
Purchase #2	$178.51	12.302%	$200.4703	$200.47	$200.45	$200.50
Purchase #3	$248.78	5.709%	$262.9829	$262.98	$263.00	$263.00
Purchase #4	$178.31	3.522%	$184.5901	$184.59	$184.60	$184.60
Purchase #5	$143.41	7.439%	$154.0783	$154.08	$154.10	$154.10
Purchase #6	$160.31	7.745%	$172.726	$172.73	$172.75	$172.70
Purchase #7	$111.80	9.646%	$122.5842	$122.58	$122.60	$122.60
7 purchase totals =	$1,221.65		$1,323.3208	$1,323.32	$1,323.40	$1,323.40