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	$224.45	11.765%	$250.8565	$250.86	$250.85	$250.90
Purchase #2	$117.87	13.512%	$133.7966	$133.80	$133.80	$133.80
Purchase #3	$110.25	8.425%	$119.5386	$119.54	$119.55	$119.50
Purchase #4	$145.40	5.194%	$152.9521	$152.95	$152.95	$153.00
Purchase #5	$225.29	13.866%	$256.5287	$256.53	$256.55	$256.50
Purchase #6	$172.55	9.690%	$189.2701	$189.27	$189.25	$189.30
Purchase #7	$54.37	9.491%	$59.5303	$59.53	$59.55	$59.50
7 purchase totals =	$1,050.18		$1,162.4729	$1,162.48	$1,162.50	$1,162.50