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	$74.77	9.695%	$82.019	$82.02	$82.00	$82.00
Purchase #2	$37.66	10.271%	$41.5281	$41.53	$41.55	$41.50
Purchase #3	$99.28	13.349%	$112.5329	$112.53	$112.55	$112.50
Purchase #4	$107.87	5.307%	$113.5947	$113.59	$113.60	$113.60
Purchase #5	$26.60	5.809%	$28.1452	$28.15	$28.15	$28.10
Purchase #6	$207.81	3.208%	$214.4765	$214.48	$214.50	$214.50
Purchase #7	$231.48	3.797%	$240.2693	$240.27	$240.25	$240.30
7 purchase totals =	$785.47		$832.5657	$832.57	$832.60	$832.50