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	$245.74	3.783%	$255.0363	$255.04	$255.05	$255.00
Purchase #2	$128.35	12.528%	$144.4297	$144.43	$144.45	$144.40
Purchase #3	$183.47	13.442%	$208.132	$208.13	$208.15	$208.10
Purchase #4	$246.78	6.852%	$263.6894	$263.69	$263.70	$263.70
Purchase #5	$45.37	8.236%	$49.1067	$49.11	$49.10	$49.10
Purchase #6	$54.60	5.250%	$57.4665	$57.47	$57.45	$57.50
Purchase #7	$223.56	7.420%	$240.1482	$240.15	$240.15	$240.10
7 purchase totals =	$1,127.87		$1,218.0088	$1,218.02	$1,218.05	$1,217.90