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	$246.35	4.680%	$257.8792	$257.88	$257.90	$257.90
Purchase #2	$141.71	13.275%	$160.522	$160.52	$160.50	$160.50
Purchase #3	$237.72	7.635%	$255.8699	$255.87	$255.85	$255.90
Purchase #4	$46.53	6.244%	$49.4353	$49.44	$49.45	$49.40
Purchase #5	$246.56	4.657%	$258.0423	$258.04	$258.05	$258.00
Purchase #6	$61.76	7.575%	$66.4383	$66.44	$66.45	$66.40
Purchase #7	$95.88	3.664%	$99.393	$99.39	$99.40	$99.40
7 purchase totals =	$1,076.51		$1,147.5800	$1,147.58	$1,147.60	$1,147.50