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	$62.41	6.597%	$66.5272	$66.53	$66.55	$66.50
Purchase #2	$54.29	4.844%	$56.9198	$56.92	$56.90	$56.90
Purchase #3	$73.55	11.542%	$82.0391	$82.04	$82.05	$82.00
Purchase #4	$239.75	6.522%	$255.3865	$255.39	$255.40	$255.40
Purchase #5	$183.53	10.874%	$203.4871	$203.49	$203.50	$203.50
Purchase #6	$92.86	5.808%	$98.2533	$98.25	$98.25	$98.30
Purchase #7	$235.55	4.654%	$246.5125	$246.51	$246.50	$246.50
7 purchase totals =	$941.94		$1,009.1255	$1,009.13	$1,009.15	$1,009.10