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	$10.63	3.223%	$10.9726	$10.97	$10.95	$11.00
Purchase #2	$139.58	7.589%	$150.1727	$150.17	$150.15	$150.20
Purchase #3	$125.96	10.177%	$138.7789	$138.78	$138.80	$138.80
Purchase #4	$217.61	7.362%	$233.6304	$233.63	$233.65	$233.60
Purchase #5	$222.59	3.604%	$230.6121	$230.61	$230.60	$230.60
Purchase #6	$210.57	11.345%	$234.4592	$234.46	$234.45	$234.50
Purchase #7	$75.51	9.144%	$82.4146	$82.41	$82.40	$82.40
7 purchase totals =	$1,002.45		$1,081.0405	$1,081.03	$1,081.00	$1,081.10