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	$74.61	10.873%	$82.7223	$82.72	$82.70	$82.70
Purchase #2	$211.87	9.265%	$231.4998	$231.50	$231.50	$231.50
Purchase #3	$45.41	7.857%	$48.9779	$48.98	$49.00	$49.00
Purchase #4	$156.92	5.175%	$165.0406	$165.04	$165.05	$165.00
Purchase #5	$213.77	4.239%	$222.8317	$222.83	$222.85	$222.80
Purchase #6	$186.28	7.223%	$199.735	$199.74	$199.75	$199.70
Purchase #7	$109.89	13.566%	$124.7977	$124.80	$124.80	$124.80
7 purchase totals =	$998.75		$1,075.6050	$1,075.61	$1,075.65	$1,075.50