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	$181.43	10.319%	$200.1518	$200.15	$200.15	$200.20
Purchase #2	$192.91	9.829%	$211.8711	$211.87	$211.85	$211.90
Purchase #3	$174.29	12.716%	$196.4527	$196.45	$196.45	$196.50
Purchase #4	$162.35	13.245%	$183.8533	$183.85	$183.85	$183.90
Purchase #5	$248.31	9.412%	$271.6809	$271.68	$271.70	$271.70
Purchase #6	$83.61	13.242%	$94.6816	$94.68	$94.70	$94.70
Purchase #7	$211.95	4.470%	$221.4242	$221.42	$221.40	$221.40
7 purchase totals =	$1,254.85		$1,380.1156	$1,380.10	$1,380.10	$1,380.30