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	$207.53	5.286%	$218.5	$218.50	$218.50	$218.50
Purchase #2	$84.66	7.553%	$91.0544	$91.05	$91.05	$91.10
Purchase #3	$82.61	12.243%	$92.7239	$92.72	$92.70	$92.70
Purchase #4	$167.75	6.491%	$178.6387	$178.64	$178.65	$178.60
Purchase #5	$187.86	4.478%	$196.2724	$196.27	$196.25	$196.30
Purchase #6	$150.58	3.644%	$156.0671	$156.07	$156.05	$156.10
Purchase #7	$60.38	11.635%	$67.4052	$67.41	$67.40	$67.40
7 purchase totals =	$941.37		$1,000.6617	$1,000.66	$1,000.60	$1,000.70