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	$151.69	8.213%	$164.1483	$164.15	$164.15	$164.10
Purchase #2	$114.42	8.228%	$123.8345	$123.83	$123.85	$123.80
Purchase #3	$142.51	7.549%	$153.2681	$153.27	$153.25	$153.30
Purchase #4	$128.74	10.833%	$142.6864	$142.69	$142.70	$142.70
Purchase #5	$66.52	6.739%	$71.0028	$71.00	$71.00	$71.00
Purchase #6	$166.27	10.177%	$183.1913	$183.19	$183.20	$183.20
Purchase #7	$166.57	12.651%	$187.6428	$187.64	$187.65	$187.60
7 purchase totals =	$936.72		$1,025.7742	$1,025.77	$1,025.80	$1,025.70