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	$80.61	3.133%	$83.1355	$83.14	$83.15	$83.10
Purchase #2	$225.98	10.177%	$248.978	$248.98	$249.00	$249.00
Purchase #3	$237.57	11.749%	$265.4821	$265.48	$265.50	$265.50
Purchase #4	$191.88	3.262%	$198.1391	$198.14	$198.15	$198.10
Purchase #5	$177.70	10.667%	$196.6553	$196.66	$196.65	$196.70
Purchase #6	$61.47	7.385%	$66.0096	$66.01	$66.00	$66.00
Purchase #7	$100.72	13.496%	$114.3132	$114.31	$114.30	$114.30
7 purchase totals =	$1,075.93		$1,172.7128	$1,172.72	$1,172.75	$1,172.70