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	$186.37	12.422%	$209.5209	$209.52	$209.50	$209.50
Purchase #2	$144.49	5.145%	$151.924	$151.92	$151.90	$151.90
Purchase #3	$71.80	13.800%	$81.7084	$81.71	$81.70	$81.70
Purchase #4	$83.69	12.540%	$94.1847	$94.18	$94.20	$94.20
Purchase #5	$38.70	3.719%	$40.1393	$40.14	$40.15	$40.10
Purchase #6	$54.97	5.471%	$57.9774	$57.98	$58.00	$58.00
Purchase #7	$177.45	7.309%	$190.4198	$190.42	$190.40	$190.40
7 purchase totals =	$757.47		$825.8745	$825.87	$825.85	$825.80