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	$101.25	12.427%	$113.8323	$113.83	$113.85	$113.80
Purchase #2	$8.41	8.754%	$9.1462	$9.15	$9.15	$9.10
Purchase #3	$223.27	4.381%	$233.0515	$233.05	$233.05	$233.10
Purchase #4	$219.94	4.866%	$230.6423	$230.64	$230.65	$230.60
Purchase #5	$168.92	8.851%	$183.8711	$183.87	$183.85	$183.90
Purchase #6	$61.50	4.826%	$64.468	$64.47	$64.45	$64.50
Purchase #7	$179.85	9.189%	$196.3764	$196.38	$196.40	$196.40
7 purchase totals =	$963.14		$1,031.3878	$1,031.39	$1,031.40	$1,031.40