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	$228.61	5.399%	$240.9527	$240.95	$240.95	$241.00
Purchase #2	$132.54	5.646%	$140.0232	$140.02	$140.00	$140.00
Purchase #3	$152.47	12.639%	$171.7407	$171.74	$171.75	$171.70
Purchase #4	$29.70	10.384%	$32.784	$32.78	$32.80	$32.80
Purchase #5	$226.43	12.815%	$255.447	$255.45	$255.45	$255.40
Purchase #6	$23.41	10.464%	$25.8596	$25.86	$25.85	$25.90
Purchase #7	$67.71	5.747%	$71.6013	$71.60	$71.60	$71.60
7 purchase totals =	$860.87		$938.4085	$938.40	$938.40	$938.40