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	$166.50	10.780%	$184.4487	$184.45	$184.45	$184.40
Purchase #2	$113.55	11.824%	$126.9762	$126.98	$127.00	$127.00
Purchase #3	$197.76	4.433%	$206.5267	$206.53	$206.55	$206.50
Purchase #4	$32.61	13.702%	$37.0782	$37.08	$37.10	$37.10
Purchase #5	$208.29	6.716%	$222.2788	$222.28	$222.30	$222.30
Purchase #6	$247.36	12.244%	$277.6468	$277.65	$277.65	$277.60
Purchase #7	$36.98	8.262%	$40.0353	$40.04	$40.05	$40.00
7 purchase totals =	$1,003.05		$1,094.9907	$1,095.01	$1,095.10	$1,094.90