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	$241.87	3.722%	$250.8724	$250.87	$250.85	$250.90
Purchase #2	$239.64	6.670%	$255.624	$255.62	$255.60	$255.60
Purchase #3	$44.72	9.793%	$49.0994	$49.10	$49.10	$49.10
Purchase #4	$105.94	10.722%	$117.2989	$117.30	$117.30	$117.30
Purchase #5	$175.58	5.851%	$185.8532	$185.85	$185.85	$185.90
Purchase #6	$250.77	4.131%	$261.1293	$261.13	$261.15	$261.10
Purchase #7	$175.48	9.188%	$191.6031	$191.60	$191.60	$191.60
7 purchase totals =	$1,234.00		$1,311.4803	$1,311.47	$1,311.45	$1,311.50