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	$200.52	5.466%	$211.4804	$211.48	$211.50	$211.50
Purchase #2	$48.62	12.478%	$54.6868	$54.69	$54.70	$54.70
Purchase #3	$226.95	5.677%	$239.834	$239.83	$239.85	$239.80
Purchase #4	$87.53	12.416%	$98.3977	$98.40	$98.40	$98.40
Purchase #5	$162.76	6.714%	$173.6877	$173.69	$173.70	$173.70
Purchase #6	$222.45	13.772%	$253.0858	$253.09	$253.10	$253.10
Purchase #7	$71.58	12.435%	$80.481	$80.48	$80.50	$80.50
7 purchase totals =	$1,020.41		$1,111.6534	$1,111.66	$1,111.75	$1,111.70