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	$82.28	12.391%	$92.4753	$92.48	$92.50	$92.50
Purchase #2	$198.68	6.606%	$211.8048	$211.80	$211.80	$211.80
Purchase #3	$164.95	4.552%	$172.4585	$172.46	$172.45	$172.50
Purchase #4	$12.57	7.449%	$13.5063	$13.51	$13.50	$13.50
Purchase #5	$131.27	4.653%	$137.378	$137.38	$137.40	$137.40
Purchase #6	$9.98	9.703%	$10.9484	$10.95	$10.95	$10.90
Purchase #7	$27.68	5.363%	$29.1645	$29.16	$29.15	$29.20
7 purchase totals =	$627.41		$667.7358	$667.74	$667.75	$667.80